14 ms·

A manifesto on shower temperature control

271 points by aarondf 4y ago

anigbrowl 4y ago
The US insists on using mixet valves wherever possible, while most other countries give you hot and cold knobs which you can adjust to taste.
- capableweb 4y ago
  Don't think this is a US-only thing, seems to vary even inside countries. Been to a lot of countries, and most showers have been without single knobs for hot/cold, but seen that too of course.
klondike_klive 4y ago
I always wondered if Britain turned out more than its fair share of safecrackers because of our traditionally crappy shower controls and how a sixteenth of a turn meant the difference of maybe 30 degrees of heat.
- pubby 4y ago
  Gosh, Britain doesn't have two shower heads per shower (one hot, one cold), does it? I know they do that for taps.
  - sam_ezeh 4y ago
    No, we don't
  - Macha 4y ago
    There are some older showers in Ireland, so I guess in the UK too, where you basically use hot/cold water taps and pull a lever which redirects the mixed tap output to a shower rather than the bath. Mostly replaced by electric showers these days though.
dusted 4y ago
But comfort areas are hugely different.. I prefer the range from scolding hot to ice-cold (I start my shower in the middle area, then prefer to turn up gradually as I get used to it until it's very hot (so hot I'd feel uncomfortable if I started at this temperature), then after a while I get very warmed through, and I turn straight to the coldest setting and enjoy the constrast from burning hot to burning cold, and that's the perfect finish for my shower. Then I step out of the ice cold shower and enjoy the warm air against my skin (even if that warm air is about 19.5C at the moment, it still feels warm in contrast to the ~2C water)
mike31fr 4y ago
> "it seems very reasonable to design a shower valve that is biased for human temperature preference" It's not that simple. Hot water temperature varies greatly from one home to another. Cold water temperature varies tremendously from summer to winter. Take a picture of your shower control for the same water temperature in winter or in summer. You will see it's not turned at the same angle, because in winter you need a lot more hot water to balance the ice cold water from outside (especially if you live in the country, it will be ice cold, trust me). As a consequence, the part of your shower control that you call "confort zone" can be almost 100% too hot or 100% too cold in another home or in another season.
fauxxenophanes 4y ago
Concerning " Why are we wasting so much potential control area on water temperatures that no one wants? ", I am a professional plumber, have been for decades and... on one occasion I was told by an aging resident of a new-build home that there " wasn't ENOUGH control area" on her brand new Moen tub/shower faucet! WOW.
PaulHoule 4y ago
I think the current ones are the way they are because the input temperature is not well controlled. I live in an old farmhouse where the cold water gets really cold in the winter and for years we've had a tankless water heater that has never worked that well but lately has gotten full of scales. We haven't tried descaling it because we're concerned that we'll kill it in the process of descaling it and won't try it unless we have a replacement lined up. All of that means that the input temperatures are poorly controlled even when the heater is working. The very large range of mixing ratios helps compensate for uncontrolled input temperatures. If the input temperature was better controlled (say with a thermostatic function) you might be able to calibrate the valves to a user-appropriate range, but barring that you'd need to put a thermostat right after the valve.
- sokoloff 4y ago
  It's obviously your risk not mine, but I wouldn't be particularly concerned with descaling a tankless with vinegar causing a problem. I'd be more concerned with the uneven heat transfer causing damage (by overheating the metal that doesn't have adequate cooling from the water [that you're intending to heat]) than I would from the descaling causing damage (or more precisely, revealing existing damage).
  - nick123567 4y ago
    You're supposed to descale them every year anyway
- gwern 4y ago
  Or to put it another way: Spolsky said that users don't use 90% of the features in any app; unfortunately, they each don't use a different 90%. You don't use 90% of the shower faucet ratio range; unfortunately, each house doesn't use a different 90% of the ratio range...
  - Gordonjcp 4y ago
    Thing is, that 90% of the range is going to mean that you and I pick a different range from "hottest" to "coldest", right? So it wouldn't be beyond the wit of man to fit a couple of setscrews, possibly accessible by popping the knob off, to set the "low" and "high" stops for the thermostat in the shower valve, right? You'd think, eh...?
joezydeco 4y ago
These devices exist. You just don't want to pay for them. https://www.kohler.com/en/products/showers/shop-shower-trims-valves/anthem-three-port-digital-thermostatic-valve-28210?skuId=28210-NA https://www.kohler.com/en/products/showers/shop-shower-trims... What you have in your shower is a cheaper anti-scald valve that just prevents super huge spikes in water temperature when the input pressure changes (i.e. your wife flushes the toilet). Like PaulHoule says, you need monitoring of input and output temps to do that. And that's technically possible, but it's complex and expensive.
- stdbrouw 4y ago
  Huh? Regular thermostatic valves do not provide perfect regulation but they do in fact provide a fairly stable output temperature regardless of cold and hot water temperature, by entirely mechanical means. I have a cheap IKEA shower control and output temp is stable for the full duration of my shower even though cold nor hot water supply is stable due to a shower drain heat recovery unit. The article is mainly about wanting the regulation to be between 35-45C instead of 15-55C.
  - achenatx 4y ago
    you can change the top end by lowering the temperature of your hot water heater. We have ours set at 120. Using a lower hot water temperature is a way to give you a wider range of useful temperatures. In texas during the summer we often take showers with no hot water (or very little hot water).
    - trynewideas 4y ago
      This isn't always feasible depending on the location, age, and type of water heater, and how many things with different temperature needs are connected to the same water heater. A tankless water heater with a feeder pump, dedicated to bathroom use and with a bathroom-installed remote control, makes this trivial. It's probably also more efficient, easier to use, and (vs. thermostatic valves) about as easy and maybe also cheaper to implement than any fussing with valves. A 30-year-old tank heater in a basement that needs a wrench to adjust a temperature that won't meaningfully change in a 2nd-floor bathroom for another half-hour, and also has to serve a dishwasher and clothes washer that might also run at higher temperatures at the same time, can't swing this as easily, or at all.
achenatx 4y ago
I have one of these grohe thermostatic valves. You can set the temperature and then use a push button to turn the shower on. The temperature is always set correctly as the on/off is separate from the temperature control. A majority of the range of the dial is usable. We still use cold water for cleaning the shower, or when you want a cold shower. During the shower, I have it set to hot, then slowly turn up the heat. This uses about half the dial's range. The big difference is the grohe costs $500 while a standard builder grader valve might be $50. https://www.build.com/product/summary/1391570?uid=3279009&jmtest=gg-gbav2_3279009&inv2=1&&source=gg-gba-pla_3279009!c6955229006!a76700685101!dc!ng&gclsrc=ds&gclsrc=ds https://www.build.com/product/summary/1391570?uid=3279009&jm... <<How does a Grohe thermostatic valve work? The thermostatic valve mixes the hot and cold water to your pre-selected temperature and reacts instantly to any changes in the pressure or temperature of the water supply by re-adjusting the mix of hot and cold water.>>
- sintezcs 4y ago
  I also have grohe thermostatic valve and enjoy it a lot! Worth every $ spent.
  - dclowd9901 4y ago
    Same, nothing but good from my experience. Just a bit finicky to install like most European hardware and fixtures. Oh and their instructions are pictures only and hilariously obtuse.
    - vl 4y ago
      Well, you can get Chinese thermostatic valve for few times cheaper.
      - dclowd9901 4y ago
        You get what you pay for in my experience.
        4y ago
Arrath 4y ago
> † The author acknowledges the recent trend of "cold showers" and considers them (a) a trend, (b) undignified, (c) a waste of some life-sustaining solidary time. Hear, hear!
- wolfram74 4y ago
  I actually find cold showers in the middle of the day quite life improving during the summer months.
- standardUser 4y ago
  I always end my showers with cool water because it works wonders for preventing dryness and itchiness on my skin. I use actually cold water to rinse my scalp. This is all very different than a shower with no hot water mixed in whatsoever. Deepening on the climate and season, water that cold can cause physical harm. In other words, I'm betting most of these "cold showerers" are actually use cool water, not anything as dramatically cold as they might want us to infer.
_yb2s 4y ago
I prefer cold showers, and have the opposite complaint. Most valves are over-optimized for 'normal' shower temp ranges, and still mix in a lot of hot water even on the coldest setting, which makes taking a really cold shower impossible.
retrac 4y ago
Ah yes, showers that have frigid, cold, and scalding settings, and not much in the way of warm. This is is usually because the hot supply is under relatively less pressure, going through a tank and more pipes. So, nice and warm means hot is almost fully open and cold almost fully closed, to get an equal mix of both. Very little room to work with. The right flow restrictor on the cold supply will make midway an even mix, and so more of the dial is useful. Very much worth the $10 the next time you have access to the plumbing.
- xenadu02 4y ago
  In a correctly plumbed system there should not be a significant pressure differential on the hot and cold sides. When done correctly (upsized feed from the utility) with balanced loops or a manifold flushing the toilet shouldn't effect shower pressure or temperature at all. I can testify to that because in our house it works that way. The only time a shower is affected is when filling the large bathtub - which fills much faster than in most homes because it has a very large feed but that's the tradeoff since there isn't enough volume from the utility in that one case. Otherwise people can flush toilets, use the kitchen sink, wash clothes, etc and showers are not affected whatsoever. Another factor is insulation - even many modern homes don't insulate the hot water pipes so even with an instant hot water heater that responds quickly you still have to pay the lost heat cost of warming the pipes and everything the pipes touch before the temperature fully stabilizes. This is a cost-saving measure - there is no reason the pipes couldn't be insulated. If you throw in a recirc pump then you can have instant hot water at every tap with very low energy cost.
  - fuzzy2 4y ago
    Even if the pressure does not change, the temperature definitely does. Currently, cold water is basically icecubes blasting out the shower head. Warm/hot water, on the other hand, is sometimes affected by a heat exchanger (district heating) malfunction.
AnthonBerg 4y ago
I have a kind of powerful dirt bike. People put “throttle cams” on them for this same reason. Usually you want small adjustments within the lower range of power. When you want the majority of power you usually want close to all of it. Throttle cams are basically an off-center circle. At lower throttle you’re pulling a smaller circle and the throttle moves less. Then when the throttle is opened up you’re pulling a bigger circle.
- MR4D 4y ago
  Now I want one of those for my car!
  - fy20 4y ago
    If you car has an Eco or Power or Sport mode this is probably what it does. On my Toyota, Power mode makes the accelerator more sensitive and Eco mode makes it less sensitive (which is great for snow). Flooring it is the same, regardless of the mode.
    - waste_monk 4y ago
      You can't even rely on this, on my car the default behaviour is that the middle of the accelerator pedals range of motion is the "sweet spot", and in fact flooring it will trigger the hill climb assist and cause the automatic transmission to go down a gear.
      - _yb2s 4y ago
        Typically there is extra resistance at the downshift position, and you already have full throttle in the current gear before engaging it.
    - sideshowb 4y ago
      I haven't owned a car with them, but I thought those modes were to control when the gear shifts happen. Sport will optimize acceleration while eco will change up sooner to save fuel
cuteboy19 4y ago
Why not simply have two separate valves for hot and cold? It's a one time expenditure! But of course this foolishness has competition: no bidets anywhere!
jjk166 4y ago
This is a result of the valve construction - you have a cold water pipe and a hot water pipe coming in, and the knob/lever is connected directly to a single valve that controls volumetrically how much the flows mix. This arrangement is both cheap to manufacture and easy to install and repair. Adding proportional control isn't too hard. Certainly an easy option would be actuating the valve electronically and just using an encoder in the knob to control it digitally. There are a lot of advantages to this, such as being able to automatically comp for actual water temperatures and customizing settings for personal preference, but it's understandable that people might feel uneasy about a cheap electronic device in close proximity to the water they are in. I'd point out that this hasn't stopped us from putting things like lights in our showers which by necessity draw much more power, but some may still be concerned. More likely it is the lack of experience with electronics that valve manufacturers and plumbers have that make them hesitant to change. For a mechanical solution, you could transmit the torque via a gearbox instead of a direct shaft. Switch gears to get higher or lower resolution control. You can even have a single set of gears with variable diameter sections to have higher precision in a fixed subsection of the range. Unfortunately this would not allow for easy adjustment for an individual installation, nonetheless different people using the same shower. The increase in manufacturing cost and installation complexity would probably not be huge, but in such a high competition commodity market it would be noticeable. But solving the real issue, a lack of fine control in the important range, is actually much easier to solve. Just make the handle on the knob longer/larger diameter. Especially if you just want to modify an existing installation, attaching an 18 inch handle onto the existing knob is something just about anyone could do in a few minutes. For precise control, grip it on the outside, for fast large changes, choke up on it. For the OEM, a design with a long handle is pennies more expensive to produce at scale, easily justified for even a very small competitive advantage. Maybe some people really like the aesthetics of a small handle, but I've never once heard someone complain a shower handle was too big. I still think the electronic controller option is better, as you can deal with other shower temperature control problems like the long heat up times of the pipes and the variable ideal water temperature at different points in the shower, but the perfect can be the enemy of the good enough. Frankly it's just weird that I can't seem to find a shower handle longer than about 6 inches available for sale right now in a quick google search.
amluto 4y ago
Yikes, the max temp is 140F. That’s dangerous and has been a code violation for a long time, for good reason: https://www.pmengineer.com/articles/94780-upc-continues-to-evolve-regarding-temperature-in-water-heaters https://www.pmengineer.com/articles/94780-upc-continues-to-e...
- Nifty3929 4y ago
  This would depend on the temperature of your hot water feed, which is likely much lower. It’s like having a speedometer in your car that goes to 180 mph.
  - Nifty3929 4y ago
    Also we have body sensors which detect acute over-temperature situations and cause us to remediate the situation before damage can occur. Usually while screaming something profane.
    - amluto 4y ago
      In case you have never been in a slippery shower or encountered anyone with one of many possible disabilities, excessively hot shower water is a genuine hazard. For example: Slow reaction time (you can get burned very quickly by excessively hot shower water) Limited sensation in some part of one’s body Balance issues or movement issues. Anything preventing one from getting to the control or out of the water very very quickly. A shower delivering 134F water is hazardous and serves no purpose.
      - userbinator 4y ago
        Who goes into an unknown shower and doesn't start out with the control at the cold end, slowly increasing it until the water is hot enough? That's like getting into a car you've never driven before and giving it full throttle right away. A shower delivering 134F water is hazardous and serves no purpose. It does if you want to clean something other than your body in it.
  - 4y ago
Zanovis 4y ago
Quick and dirty solution: find the optimal position for the valve(s), mark where they are relative to their base, and open the valves to that position each time
- op00to 4y ago
  My cold water temperature fluctuates with the outdoor air temperature, doesn't everyone's?
gorgoiler 4y ago
As a friendly heads up to anyone exploring this space — temperature control is a complex dynamic between many components, chiefly the mixing valve, any local thermostatic dampers in the valve (rarer, but definitely a feature of high end mixers), and the source of hot water itself. Mixer taps are not simply mixing hot water at temperature H and cold water at temperature C. The temperature H which your hot water source is capable of reaching is highly variable and certainly not constant. Higher flow for example reduces temperature as more cold water cools the heater. Heaters also cut out and oscillate as they overload. Throughout the year the C temperature may also fluctuate by several degrees in a way that can trigger non linear effects in the hot water generator. (This is all assuming you have a just-in-time hot water source of course — more common in Europe than, say, NYC apartment blocks.) Study the whole system and be prepared for unexpected non linearity everywhere. Heat loss per foot of pipe is a real thing, as is thermal damping of uninsulated tubing, to give two more examples. If you can model the system then next up, you might try your hand at predicting the weather.
- thrwawy74 4y ago
  So we need like a capacitor for hot water at the shower head.
  - hnuser123456 4y ago
    Or just active control? Set a desired output water temp, and let a computer constantly fiddle with the valves slightly to keep the output constant. Monitoring the current temp of the input lines would help but not be necessary. I mostly don't like that every few minutes, I have to turn down the cold water a smidge, as fresher colder water from the ground comes up through the pipe. My shower has two valves for hot and cold separate, so I turn the hot water all the way on, then add just enough cold water to achieve human shower temps at full pressure.
    - oakwhiz 4y ago
      Interestingly, control valves employed in this way tend to wear out very quickly or else they are slow and expensive so that they can be made more durable. Anybody working on this needs to hit that "good, fast and cheap" triple point. This is why wax motors are commonly used as valve actuators since the only calibrations are the wax mixture, the mechanical force applicator, and the thermal resistance of various components in contact with each other
teaearlgraycold 4y ago
Why does my kettle have a thermometer but my shower does not?
- balfirevic 4y ago
  Because you (or your landlord) bought one without it - showers with thermometers do exist.
  - 0x457 4y ago
    Moreover, showers with purely mechanical thermostats exist.
- crazygringo 4y ago
  Because your kettle is electrically heated but your shower mixes hot and cold mechanically. That said, you can pay $$$ for an electrically controlled shower with a thermostat. And also worry about the electronics and motor breaking at some point.
- midoridensha 4y ago
  Because you're American. In other countries, showers have temperature settings on the controls.
TheChaplain 4y ago
Reminds me of the time I went to England, ended up in a cheaper hotel with a wash basin that had two taps on each side, hot and cold. Although it was a real pain, what really shocked me was the carpet floor in the shower room...
PicassoCTs 4y ago
Not on the screen, is that pipes are a non linear heat regulation plant. https://en.wikipedia.org/wiki/Plant_(control_theory) https://en.wikipedia.org/wiki/Plant_(control_theory) Means, demand for warmth is not fullfilled, until the heat has warmed up the pipes, and then its over fullfilled, to the point you regulate towards. Same goes towards the other direction. Cold first cools down the pipe before becoming fully cold..
bluSCALE4 4y ago
I'm actually installing a thermostatic valve today to go with a recirculating pump I have setup on an electric heat pump water heater. I'm going to be installing it exactly like this guy with an expansion tank. Does anyone see a problem with this layout? Apparently, his doesn't work. https://www.amazon.com/review/R3NQCKZCEQLLLC/ref=cm_cr_srp_d_rdp_perm?ie=UTF8 https://www.amazon.com/review/R3NQCKZCEQLLLC/ref=cm_cr_srp_d...
- ars 4y ago
  Get this and install by the heater: https://smile.amazon.com/dp/B08R1HKZ78/ https://smile.amazon.com/dp/B08R1HKZ78/ or this: https://smile.amazon.com/gp/product/B09V7MDZHF https://smile.amazon.com/gp/product/B09V7MDZHF under the sink. There's a remote available also. By sure and carefully read the details - there is an "E" model, be sure and understand the difference and pick the right kind for your setup.
  - bluSCALE4 4y ago
    I have everything I need, I just need the position of the expansion tank confirmed.
    - ars 4y ago
      I'm kind of confused on the question since you said "expansion tank". Which I guess is used because of a check valve - but that's if you put a check valve to the cold water back to the city, which isn't really part of a recirculation installation. A check valve for the recirculation should not need an expansion tank. A heat pump water heater will not work well with this mixing valve - just pipe the hot water direct to where it's needed, don't mix it with cold. A heat pump doesn't really want to make very very hot water, unlike fuel heat. This valve is meant for you to heat the water extra extra hot, then mix it. It's used when you have a small tank, and a lot of usage. It wastes energy, but gives you more hot water. It's just a bad idea to mix with a heat pump which much prefers lower water temperature. And using this mixing valve with a recirculating pump can't possibly work. This valve adds cold water, but a recirculating valve circulates the same volume of water, and does not add any. There's simply no way that it can work - it's impossible. Do you get why? Are you planning on having the recirculating pump always on, or do you prefer to press a button and wait a short time for the hot water? I ask because if you prefer the first type, you really want a dedicated return pipe for it. The second type can use the existing cold water pipe for return, but even then works much better with a dedicated return. Without a dedicated return line you never have cold water, the cold water is always warm because when you turn on the cold water, some hot water flows via the pump, and to your faucet. The expansion tank should be connected directly to the hot output of the heater before any mixing valves or recirculating stuff.
deathanatos 4y ago
On a FIRST robot, we needed something similar. There's "full reverse", "full forward" and "I need fine control", and the original mapping of joystick to wheel motors was linear. It didn't work well for "fine control". We ended up with motor = joystick³ (or some other odd, greater than 1 power; it might have been ⁵). Then you fix, via coefficients, the endpoints of the equation such that the lowest joystick value hits the full-reverse motor setting, and vice versa for forward. The exponent dampens the curve near zero, so there's more "joystick space" spent on the very slow speeds for the fine control, but the operator can still ask for max speed if they want it. (With joysticks, you also have to deadzone the middle, as "operator has centered the joystick" will sometimes report joystick values of 1 or -1, instead of 0. Or buy a better joystick.) I'm not 100% sure I'd apply this to a shower: max hot on my shower is hot, I don't usually ever want it. And I wouldn't want to scald someone. For a long while, our shower was not the typical tiny goldilocks zone surrounded by ice and lava: … it never really got above "lukewarm", even at max. We had the shower valve replaced and it works better now. (And, apparently, as I learned, there's a mixing valve at the hot water heater: i.e., the hot to the shower is not direct from the water heater, like I had imagined. We raised the temp there, slightly.)
- pc86 4y ago
  When my wife and I met she lived in an apartment with an amazing shower. The pressure was good but the temperature was fantastic. I had never had an apartment shower with water that got so hot. I barely even went half-way on the knob before I was turning it down. I asked about it and her response was "oh yeah I complained to my dad and he looked at the heater, there was something on it that he broke off." Turns out there was some piece of plastic or something put on by the landlord to limit the top temperature of the water, so he took it off. It didn't keep the hot water from running out but when you had it, it was great.
- waste_monk 4y ago
  >(And, apparently, as I learned, there's a mixing valve at the hot water heater: i.e., the hot to the shower is not direct from the water heater, like I had imagined. We raised the temp there, slightly.) When we changed from instant hot water to water tank + heat pump, the guy said the tempering valve was a safety thing (IIRC ours was set to 60 degrees Celsius by default, but could go up or down about 10 degree either way). That is, if you accidentally step in the shower with only hot water on you'll still hurt yourself but the damage will be limited to "strong profanity and aloe vera" instead of "you've won a stay in the burn ward". Although saying this, I did a quick bit of research and found that 60 may still be too high [1]. I have an IR thermometer so I think I'll measure the temperature of my shower (after any loss from pipes etc.) and see if the tempering valve needs adjusting down. [1] mild nsfw - image of scalded foot https://whywait.com.au/a-serious-hot-water-burn-occurs-in-one-second/ https://whywait.com.au/a-serious-hot-water-burn-occurs-in-on...
yehudalouis 4y ago
Just add a gear affixed to the handle, and then a second gear mated with that, and find the gearing ratio that allows the granular/sensitive inputs you want.
russellbeattie 4y ago
The amount of water wasted waiting for the water to warm up must be astronomical. In my place it can take three or four minutes of the water running to get warm - if not longer - and I don't think that's atypical. Multiply this by 7 days a week by everyone who showers in California alone and it seems like an issue that should get some serious attention.
- rconti 4y ago
  It's particularly bad with my tankless hot water heater that apparently doesn't even turn on for 15 seconds, and then you wait for the hot water to get to the shower. I swear the whole thing takes 60-90 seconds, and I live in a tiny house. I can't fathom what the hot water is doing on its way to the faucet. (well, yeah, some of that time is also spent heating the cold uninsulated under-house pipes).
  - 0x457 4y ago
    I swear I had to wait nearly 5 minutes every morning before _warm_ water starts coming out, and our tankless heater was a wall away from shower.
standardUser 4y ago
I'm obsessed with showers and also wonder why we are so spectacularly bad at making consistently good showerheads with consistently good pressure and temperature control. One issue the author overlooks is that we have minimal control over the temperature of the cold water, and this temperature fluctuates throughout the year (at least here in NY, not so much where I lived in SF). As a result, the range of the dial I use changes from summer to winter. There are hot parts of the dial I use everyday in the winter that would simply burn me if I used them in the summer. Temperature can even change during the course of the shower! I notice this mostly in the winter. I speculate this is due to the cold water in my building pipes being used up and then replaced by the truly cold water from underground. I once tried to shower with that icy water when the hot water went out (just before a big trip) and I managed to completely numb my lower body (I did not have the fortitude to try and shower my upper body too).
- aidenn0 4y ago
  The water pipes to my shower go through an exterior west-facing wall. Mornings in the winter, the first half-gallon or so of water is basically the same temperature as the outside air-temperature. Evenings in summer, the first half-gallon can be painfully hot, even from the cold-water supply.
- culebron21 4y ago
  We have central hot water, and in winter hot water is incredibly hot, because the thermo-power station runs high.
aliceryhl 4y ago
Our shower has two dials: temperature and pressure. The temperature dial has a specific temperature that it will "snap" to. (When increasing temperature, it will stop there unless you hold in a button. It doesn't snap when decreasing the temperature.) Generally, I find the temperature it snaps to quite pleasant, so I just put it at the snap temperature and then open for the water with the other dial.
farhanhubble 4y ago
Very interesting exploration. However does this assumption really hold for the commonly used valves: >Since temperature has a nearly >linear relationship with control >rotation I thought the valves have circular openings and the flow changes non linearly, which I have always experienced too. Just a few days back I was thinking of why no one has thought about linear controls.
jnellis 4y ago
I've noticed you don't see the pivot type valves anymore where you can just go up and over to hot right away. Most shower valves now are turn-throughs, where you start at cold and go up to hot. Having installed a few now, I think this has to do with the federal law for having a scald prevention device in the valves control (much like having a low-flo device in shower heads.) Both instances, they are plastic and so you can remove them or adjust them later. I think it's just easier to make a scald prevention device for a turn-through valve than a pivot valve and that's why most shower handles suck today. It's just a tiny plastic piece that impedes how far into the hot range the handle will go.
ars 4y ago
People should stop buying pressure-balance shower valves, and switch to thermostatic valves. My shower valve is actually marked in degrees on the dial, and you set it to exactly the temperature you want and then don't mess with it - it will adjust as hotter water arrives.
PebblesRox 4y ago
I was house-sitting one time and took several miserable showers before realizing that the temperature dial started out on hot and got colder the farther I turned it!
theboywho 4y ago
Thinking from first principes, what about a shower handle that copies how air conditioners and heating work, something like a screen showing the exact temperature of the water with an Up and Down buttons to control the temperature.
- loandbehold 4y ago
  These exist: https://www.build.com/digital-showers/c131744?facets=application_s:Digital%20Shower%20Controls https://www.build.com/digital-showers/c131744?facets=applica...
deleted 4y ago
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hbarka 4y ago
I loved the seriousness of this manifesto. A most-pressing issue indeed. The search for the better shower handle will be squabbled just like the quest for a better mousetrap. My two cents—a cam in the shower handle could follow that curve.
dclowd9901 4y ago
Just bought a Grohe thermostatic shower control and it’s one of the best things I’ve ever bought. Saves water and keeps the temperature comfortable. Highly recommend a thermostatic control.
- culebron21 4y ago
  I saw these in Germany and bought one for my home when I got fed up of adjusting the shower at home. I told my parents, -- they'd have the same problem, and one would shuffle the toilet while the other was taking shower -- but they didn't bother, until I just bought and installed one for them as a gift.
whatyearisit 4y ago
I've focused on this problem for some time too. The ultimate solution was to buy a color changing shower head from LIDL. This made it so easy to always be in the right temperature zone when taking a shower. The shower head has lighting that turns to green when the temperature is between 34-38C°. It's red when the temperature is above 38°, and turns to blue when it's below 34°C. It also shows the current temperature as a display which you can see while you are under the shower. The sensor setup also seems to be powered by the stream that flows through the shower head and only turns on when water is running. I hope this helps.
cirrus3 4y ago
Why is there no mention of the water heater temp control? If the water is way too hot on one end, you need to calibrate your input before worrying about the control of the output.
afinlayson 4y ago
This is one of many problems with the lack of innovation in the home in the last 40 years. Being a former IOT UXE I've been fascinated with this space. It's too bad my pitches never took off.
- midoridensha 4y ago
  There's no lack of innovation in the home. It's just that Americans refuse to adopt any of the innovations that have become commonplace in the last 40 years.
rconti 4y ago
2 side-rants: * Physical shower controls themselves. The typical US single-handle shower control is awful. Maybe I'm stupid, but it's never intuitive to me which side is hot and which side is cold. Much of the time the handle is pointing down, so you have to visualize an arrow extending through the top of the control, pointing left (hot) when the handle is on the bottom right. Sometimes they point entirely different directions, or the rotational positions of off, cold, hot make no sense at all. As I write this, it occurs to me that it's probably obvious that cold is always closest to "off", and "full on" is always full hot, but I'm over 40 and this has never occurred to me until now, so it can't be just me. Anyway, for whatever reason, when they're not labeled, i've never been able to 'remember' which side is hot and which side is cold. Again, maybe it's just me, but I've never had any other such dyslexic tendencies outside of faucet control. I think in my head "C" is on the left because it places C and H in alphabetical order? * Tankless hot water heaters. I want to like them. I've had them in my last 2 houses, covering the past 12 years. I can't imagine buying a water heater with a tank, but... The (central) tankless heaters take 15 seconds to turn on, and the water takes forever to make its way across my tiny house. So much water and time is wasted. And they shut off after some minimum flow rate. So if you try to use 'too little' hot mix (hot water heater set 'too high' or cold water input too warm, say, in the summer), the water heater decides to click off.. which you only notice 20 seconds later as the hot water trickles out of the pipes, and now you have to wash, rinse, repeat the whole awful cycle of turning the handle to full hot, waiting for hot water again, turning it down, but hoping you didn't turn it down too far. I've turned the hot water heater down as low as it'll go without much noticeable difference in this behavior in either house. Perhaps because the minimum flow rate actually depends on the setpoint of the hot water, which would make sense. It's worse in the summer. It's only a problem I have in 10% of my showers, but it drives me nuts.
bschwindHN 4y ago
I've been enjoying my digitally controlled shower temperature for years now. Japan figured this out a long time ago. I know the the temperature I like for a given season, and have up/down buttons to adjust it if needed.
jameshart 4y ago
Much of the confusion in this thread comes down to the fact that in the US, the standard shower valve is a 'pressure-balanced' valve, which allows you to select a flow-ratio between hot and cold feeds, but does not in itself maintain any particular temperature - it just ensures that in the event of pressure changes on one or other feed, the overall mix is maintained (preventing temperature spikes if someone flushes a toilet). Whereas in many other parts of the world, the standard shower valve is a 'thermostatic mixing valve', which allows you to select a temperature, and balances the inputs to achieve that desired temperature mark. Note that if you go to, say, HomeDepot.com, and look at shower faucets, you will not find thermostatic mixing valves. Only pressure balanced. The only thermostatic component in conventional american shower valves is an anti-scald-cutoff. Thermostatic valves do exist, but they're not the ones that are bundled into showers and that therefore get employed by the average landlord who is grabbing the cheap standard parts off the shelf. Thermostatic is a premium option, and not one that even crops up in the search result filters for showers. So most Americans have simply no idea that thermostatic valves are a thing. Whereas if you go to, say, diy.com (which is the store of B&Q, an equivalent store in the UK), and look up showers, you will find all the basic 'mixer showers' have thermostatic valves.
- saghm 4y ago
  > So most Americans have simply no idea that thermostatic valves are a thing. Having very limited travel experience outside the US, my mental model of what the temperature control on showers was supposed to be doing was thermostatic, and I just assumed that they were just bad at it. You may have just explained one of my longest running minor peeves, which is that I've always found it basically impossible to maintain a shower temperature I find comfortable without needing to make adjustments. Given that I don't own my home at this time, I probably can't do anything about it any time soon, but at least from now on when I have to deal with the fluctuations in temperature I'll know that I'm not crazy and this is actually expected behavior.
  - account42 4y ago
    It gets even worse when the water heating is flow activated (switching between 0 and 100%) and your faucet/shower head is too gunked up to allow for enough flow from at the desired hot/cold mix.
deleted 4y ago
[deleted]
mlnhd 4y ago
I want a valve that turns off the hot water supply completely after 10 minutes
ab8 4y ago
I want to be able to control flow and temperature separately.
throwaway892238 4y ago
There is a special kind of engineering that goes into luxury cars to get the windows to make a pleasing sound when you roll them up. That's the kind of engineering it takes to make a shower that only produces comfortable temperature water.
culebron21 4y ago
Thermostatic shower mixer by Grohe and some more manufacturers fixes this problem, and also 1) when someone shuffles the toilet on the same pipe, 2) when you use hot water from a heating tank on the cold pipe. https://duckduckgo.com/?t=ffab&q=grohe+thermostatic+shower&ia=web https://duckduckgo.com/?t=ffab&q=grohe+thermostatic+shower&i...

271 points by aarondf 4y ago

The US insists on using mixet valves wherever possible, while most other countries give you hot and cold knobs which you can adjust to taste.

capableweb 4y ago
Don't think this is a US-only thing, seems to vary even inside countries. Been to a lot of countries, and most showers have been without single knobs for hot/cold, but seen that too of course.

klondike_klive 4y ago

I always wondered if Britain turned out more than its fair share of safecrackers because of our traditionally crappy shower controls and how a sixteenth of a turn meant the difference of maybe 30 degrees of heat.

pubby 4y ago
Gosh, Britain doesn't have two shower heads per shower (one hot, one cold), does it? I know they do that for taps.
- sam_ezeh 4y ago
  No, we don't
- Macha 4y ago
  There are some older showers in Ireland, so I guess in the UK too, where you basically use hot/cold water taps and pull a lever which redirects the mixed tap output to a shower rather than the bath. Mostly replaced by electric showers these days though.

dusted 4y ago

But comfort areas are hugely different.. I prefer the range from scolding hot to ice-cold (I start my shower in the middle area, then prefer to turn up gradually as I get used to it until it's very hot (so hot I'd feel uncomfortable if I started at this temperature), then after a while I get very warmed through, and I turn straight to the coldest setting and enjoy the constrast from burning hot to burning cold, and that's the perfect finish for my shower. Then I step out of the ice cold shower and enjoy the warm air against my skin (even if that warm air is about 19.5C at the moment, it still feels warm in contrast to the ~2C water)

mike31fr 4y ago

> "it seems very reasonable to design a shower valve that is biased for human temperature preference" It's not that simple. Hot water temperature varies greatly from one home to another. Cold water temperature varies tremendously from summer to winter. Take a picture of your shower control for the same water temperature in winter or in summer. You will see it's not turned at the same angle, because in winter you need a lot more hot water to balance the ice cold water from outside (especially if you live in the country, it will be ice cold, trust me). As a consequence, the part of your shower control that you call "confort zone" can be almost 100% too hot or 100% too cold in another home or in another season.

fauxxenophanes 4y ago

Concerning " Why are we wasting so much potential control area on water temperatures that no one wants? ", I am a professional plumber, have been for decades and... on one occasion I was told by an aging resident of a new-build home that there " wasn't ENOUGH control area" on her brand new Moen tub/shower faucet! WOW.

PaulHoule 4y ago

I think the current ones are the way they are because the input temperature is not well controlled. I live in an old farmhouse where the cold water gets really cold in the winter and for years we've had a tankless water heater that has never worked that well but lately has gotten full of scales. We haven't tried descaling it because we're concerned that we'll kill it in the process of descaling it and won't try it unless we have a replacement lined up. All of that means that the input temperatures are poorly controlled even when the heater is working. The very large range of mixing ratios helps compensate for uncontrolled input temperatures. If the input temperature was better controlled (say with a thermostatic function) you might be able to calibrate the valves to a user-appropriate range, but barring that you'd need to put a thermostat right after the valve.

sokoloff 4y ago
It's obviously your risk not mine, but I wouldn't be particularly concerned with descaling a tankless with vinegar causing a problem. I'd be more concerned with the uneven heat transfer causing damage (by overheating the metal that doesn't have adequate cooling from the water [that you're intending to heat]) than I would from the descaling causing damage (or more precisely, revealing existing damage).
- nick123567 4y ago
  You're supposed to descale them every year anyway
gwern 4y ago
Or to put it another way: Spolsky said that users don't use 90% of the features in any app; unfortunately, they each don't use a different 90%. You don't use 90% of the shower faucet ratio range; unfortunately, each house doesn't use a different 90% of the ratio range...
- Gordonjcp 4y ago
  Thing is, that 90% of the range is going to mean that you and I pick a different range from "hottest" to "coldest", right? So it wouldn't be beyond the wit of man to fit a couple of setscrews, possibly accessible by popping the knob off, to set the "low" and "high" stops for the thermostat in the shower valve, right? You'd think, eh...?

joezydeco 4y ago

These devices exist. You just don't want to pay for them. https://www.kohler.com/en/products/showers/shop-shower-trims-valves/anthem-three-port-digital-thermostatic-valve-28210?skuId=28210-NA https://www.kohler.com/en/products/showers/shop-shower-trims... What you have in your shower is a cheaper anti-scald valve that just prevents super huge spikes in water temperature when the input pressure changes (i.e. your wife flushes the toilet). Like PaulHoule says, you need monitoring of input and output temps to do that. And that's technically possible, but it's complex and expensive.

stdbrouw 4y ago
Huh? Regular thermostatic valves do not provide perfect regulation but they do in fact provide a fairly stable output temperature regardless of cold and hot water temperature, by entirely mechanical means. I have a cheap IKEA shower control and output temp is stable for the full duration of my shower even though cold nor hot water supply is stable due to a shower drain heat recovery unit. The article is mainly about wanting the regulation to be between 35-45C instead of 15-55C.
- achenatx 4y ago
  you can change the top end by lowering the temperature of your hot water heater. We have ours set at 120. Using a lower hot water temperature is a way to give you a wider range of useful temperatures. In texas during the summer we often take showers with no hot water (or very little hot water).
  - trynewideas 4y ago
    This isn't always feasible depending on the location, age, and type of water heater, and how many things with different temperature needs are connected to the same water heater. A tankless water heater with a feeder pump, dedicated to bathroom use and with a bathroom-installed remote control, makes this trivial. It's probably also more efficient, easier to use, and (vs. thermostatic valves) about as easy and maybe also cheaper to implement than any fussing with valves. A 30-year-old tank heater in a basement that needs a wrench to adjust a temperature that won't meaningfully change in a 2nd-floor bathroom for another half-hour, and also has to serve a dishwasher and clothes washer that might also run at higher temperatures at the same time, can't swing this as easily, or at all.

achenatx 4y ago

I have one of these grohe thermostatic valves. You can set the temperature and then use a push button to turn the shower on. The temperature is always set correctly as the on/off is separate from the temperature control. A majority of the range of the dial is usable. We still use cold water for cleaning the shower, or when you want a cold shower. During the shower, I have it set to hot, then slowly turn up the heat. This uses about half the dial's range. The big difference is the grohe costs $500 while a standard builder grader valve might be $50. https://www.build.com/product/summary/1391570?uid=3279009&jmtest=gg-gbav2_3279009&inv2=1&&source=gg-gba-pla_3279009!c6955229006!a76700685101!dc!ng&gclsrc=ds&gclsrc=ds https://www.build.com/product/summary/1391570?uid=3279009&jm... <<How does a Grohe thermostatic valve work? The thermostatic valve mixes the hot and cold water to your pre-selected temperature and reacts instantly to any changes in the pressure or temperature of the water supply by re-adjusting the mix of hot and cold water.>>

sintezcs 4y ago
I also have grohe thermostatic valve and enjoy it a lot! Worth every $ spent.
- dclowd9901 4y ago
  Same, nothing but good from my experience. Just a bit finicky to install like most European hardware and fixtures. Oh and their instructions are pictures only and hilariously obtuse.
  - vl 4y ago
    Well, you can get Chinese thermostatic valve for few times cheaper.
    - dclowd9901 4y ago
      You get what you pay for in my experience.
      - 4y ago

Arrath 4y ago

> † The author acknowledges the recent trend of "cold showers" and considers them (a) a trend, (b) undignified, (c) a waste of some life-sustaining solidary time. Hear, hear!

wolfram74 4y ago
I actually find cold showers in the middle of the day quite life improving during the summer months.
standardUser 4y ago
I always end my showers with cool water because it works wonders for preventing dryness and itchiness on my skin. I use actually cold water to rinse my scalp. This is all very different than a shower with no hot water mixed in whatsoever. Deepening on the climate and season, water that cold can cause physical harm. In other words, I'm betting most of these "cold showerers" are actually use cool water, not anything as dramatically cold as they might want us to infer.

_yb2s 4y ago

I prefer cold showers, and have the opposite complaint. Most valves are over-optimized for 'normal' shower temp ranges, and still mix in a lot of hot water even on the coldest setting, which makes taking a really cold shower impossible.

retrac 4y ago

Ah yes, showers that have frigid, cold, and scalding settings, and not much in the way of warm. This is is usually because the hot supply is under relatively less pressure, going through a tank and more pipes. So, nice and warm means hot is almost fully open and cold almost fully closed, to get an equal mix of both. Very little room to work with. The right flow restrictor on the cold supply will make midway an even mix, and so more of the dial is useful. Very much worth the $10 the next time you have access to the plumbing.

xenadu02 4y ago
In a correctly plumbed system there should not be a significant pressure differential on the hot and cold sides. When done correctly (upsized feed from the utility) with balanced loops or a manifold flushing the toilet shouldn't effect shower pressure or temperature at all. I can testify to that because in our house it works that way. The only time a shower is affected is when filling the large bathtub - which fills much faster than in most homes because it has a very large feed but that's the tradeoff since there isn't enough volume from the utility in that one case. Otherwise people can flush toilets, use the kitchen sink, wash clothes, etc and showers are not affected whatsoever. Another factor is insulation - even many modern homes don't insulate the hot water pipes so even with an instant hot water heater that responds quickly you still have to pay the lost heat cost of warming the pipes and everything the pipes touch before the temperature fully stabilizes. This is a cost-saving measure - there is no reason the pipes couldn't be insulated. If you throw in a recirc pump then you can have instant hot water at every tap with very low energy cost.
- fuzzy2 4y ago
  Even if the pressure does not change, the temperature definitely does. Currently, cold water is basically icecubes blasting out the shower head. Warm/hot water, on the other hand, is sometimes affected by a heat exchanger (district heating) malfunction.

AnthonBerg 4y ago

I have a kind of powerful dirt bike. People put “throttle cams” on them for this same reason. Usually you want small adjustments within the lower range of power. When you want the majority of power you usually want close to all of it. Throttle cams are basically an off-center circle. At lower throttle you’re pulling a smaller circle and the throttle moves less. Then when the throttle is opened up you’re pulling a bigger circle.

MR4D 4y ago
Now I want one of those for my car!
- fy20 4y ago
  If you car has an Eco or Power or Sport mode this is probably what it does. On my Toyota, Power mode makes the accelerator more sensitive and Eco mode makes it less sensitive (which is great for snow). Flooring it is the same, regardless of the mode.
  - waste_monk 4y ago
    You can't even rely on this, on my car the default behaviour is that the middle of the accelerator pedals range of motion is the "sweet spot", and in fact flooring it will trigger the hill climb assist and cause the automatic transmission to go down a gear.
    - _yb2s 4y ago
      Typically there is extra resistance at the downshift position, and you already have full throttle in the current gear before engaging it.
  - sideshowb 4y ago
    I haven't owned a car with them, but I thought those modes were to control when the gear shifts happen. Sport will optimize acceleration while eco will change up sooner to save fuel

cuteboy19 4y ago

Why not simply have two separate valves for hot and cold? It's a one time expenditure! But of course this foolishness has competition: no bidets anywhere!

jjk166 4y ago

This is a result of the valve construction - you have a cold water pipe and a hot water pipe coming in, and the knob/lever is connected directly to a single valve that controls volumetrically how much the flows mix. This arrangement is both cheap to manufacture and easy to install and repair. Adding proportional control isn't too hard. Certainly an easy option would be actuating the valve electronically and just using an encoder in the knob to control it digitally. There are a lot of advantages to this, such as being able to automatically comp for actual water temperatures and customizing settings for personal preference, but it's understandable that people might feel uneasy about a cheap electronic device in close proximity to the water they are in. I'd point out that this hasn't stopped us from putting things like lights in our showers which by necessity draw much more power, but some may still be concerned. More likely it is the lack of experience with electronics that valve manufacturers and plumbers have that make them hesitant to change. For a mechanical solution, you could transmit the torque via a gearbox instead of a direct shaft. Switch gears to get higher or lower resolution control. You can even have a single set of gears with variable diameter sections to have higher precision in a fixed subsection of the range. Unfortunately this would not allow for easy adjustment for an individual installation, nonetheless different people using the same shower. The increase in manufacturing cost and installation complexity would probably not be huge, but in such a high competition commodity market it would be noticeable. But solving the real issue, a lack of fine control in the important range, is actually much easier to solve. Just make the handle on the knob longer/larger diameter. Especially if you just want to modify an existing installation, attaching an 18 inch handle onto the existing knob is something just about anyone could do in a few minutes. For precise control, grip it on the outside, for fast large changes, choke up on it. For the OEM, a design with a long handle is pennies more expensive to produce at scale, easily justified for even a very small competitive advantage. Maybe some people really like the aesthetics of a small handle, but I've never once heard someone complain a shower handle was too big. I still think the electronic controller option is better, as you can deal with other shower temperature control problems like the long heat up times of the pipes and the variable ideal water temperature at different points in the shower, but the perfect can be the enemy of the good enough. Frankly it's just weird that I can't seem to find a shower handle longer than about 6 inches available for sale right now in a quick google search.

amluto 4y ago

Yikes, the max temp is 140F. That’s dangerous and has been a code violation for a long time, for good reason: https://www.pmengineer.com/articles/94780-upc-continues-to-evolve-regarding-temperature-in-water-heaters https://www.pmengineer.com/articles/94780-upc-continues-to-e...

Nifty3929 4y ago
This would depend on the temperature of your hot water feed, which is likely much lower. It’s like having a speedometer in your car that goes to 180 mph.
- Nifty3929 4y ago
  Also we have body sensors which detect acute over-temperature situations and cause us to remediate the situation before damage can occur. Usually while screaming something profane.
  - amluto 4y ago
    In case you have never been in a slippery shower or encountered anyone with one of many possible disabilities, excessively hot shower water is a genuine hazard. For example: Slow reaction time (you can get burned very quickly by excessively hot shower water) Limited sensation in some part of one’s body Balance issues or movement issues. Anything preventing one from getting to the control or out of the water very very quickly. A shower delivering 134F water is hazardous and serves no purpose.
    - userbinator 4y ago
      Who goes into an unknown shower and doesn't start out with the control at the cold end, slowly increasing it until the water is hot enough? That's like getting into a car you've never driven before and giving it full throttle right away. A shower delivering 134F water is hazardous and serves no purpose. It does if you want to clean something other than your body in it.
- 4y ago

Zanovis 4y ago

Quick and dirty solution: find the optimal position for the valve(s), mark where they are relative to their base, and open the valves to that position each time

op00to 4y ago
My cold water temperature fluctuates with the outdoor air temperature, doesn't everyone's?

gorgoiler 4y ago

As a friendly heads up to anyone exploring this space — temperature control is a complex dynamic between many components, chiefly the mixing valve, any local thermostatic dampers in the valve (rarer, but definitely a feature of high end mixers), and the source of hot water itself. Mixer taps are not simply mixing hot water at temperature H and cold water at temperature C. The temperature H which your hot water source is capable of reaching is highly variable and certainly not constant. Higher flow for example reduces temperature as more cold water cools the heater. Heaters also cut out and oscillate as they overload. Throughout the year the C temperature may also fluctuate by several degrees in a way that can trigger non linear effects in the hot water generator. (This is all assuming you have a just-in-time hot water source of course — more common in Europe than, say, NYC apartment blocks.) Study the whole system and be prepared for unexpected non linearity everywhere. Heat loss per foot of pipe is a real thing, as is thermal damping of uninsulated tubing, to give two more examples. If you can model the system then next up, you might try your hand at predicting the weather.

thrwawy74 4y ago
So we need like a capacitor for hot water at the shower head.
- hnuser123456 4y ago
  Or just active control? Set a desired output water temp, and let a computer constantly fiddle with the valves slightly to keep the output constant. Monitoring the current temp of the input lines would help but not be necessary. I mostly don't like that every few minutes, I have to turn down the cold water a smidge, as fresher colder water from the ground comes up through the pipe. My shower has two valves for hot and cold separate, so I turn the hot water all the way on, then add just enough cold water to achieve human shower temps at full pressure.
  - oakwhiz 4y ago
    Interestingly, control valves employed in this way tend to wear out very quickly or else they are slow and expensive so that they can be made more durable. Anybody working on this needs to hit that "good, fast and cheap" triple point. This is why wax motors are commonly used as valve actuators since the only calibrations are the wax mixture, the mechanical force applicator, and the thermal resistance of various components in contact with each other

teaearlgraycold 4y ago

Why does my kettle have a thermometer but my shower does not?

balfirevic 4y ago
Because you (or your landlord) bought one without it - showers with thermometers do exist.
- 0x457 4y ago
  Moreover, showers with purely mechanical thermostats exist.
crazygringo 4y ago
Because your kettle is electrically heated but your shower mixes hot and cold mechanically. That said, you can pay $$$ for an electrically controlled shower with a thermostat. And also worry about the electronics and motor breaking at some point.
midoridensha 4y ago
Because you're American. In other countries, showers have temperature settings on the controls.

TheChaplain 4y ago

Reminds me of the time I went to England, ended up in a cheaper hotel with a wash basin that had two taps on each side, hot and cold. Although it was a real pain, what really shocked me was the carpet floor in the shower room...

PicassoCTs 4y ago

Not on the screen, is that pipes are a non linear heat regulation plant. https://en.wikipedia.org/wiki/Plant_(control_theory) https://en.wikipedia.org/wiki/Plant_(control_theory) Means, demand for warmth is not fullfilled, until the heat has warmed up the pipes, and then its over fullfilled, to the point you regulate towards. Same goes towards the other direction. Cold first cools down the pipe before becoming fully cold..

bluSCALE4 4y ago

I'm actually installing a thermostatic valve today to go with a recirculating pump I have setup on an electric heat pump water heater. I'm going to be installing it exactly like this guy with an expansion tank. Does anyone see a problem with this layout? Apparently, his doesn't work. https://www.amazon.com/review/R3NQCKZCEQLLLC/ref=cm_cr_srp_d_rdp_perm?ie=UTF8 https://www.amazon.com/review/R3NQCKZCEQLLLC/ref=cm_cr_srp_d...

ars 4y ago
Get this and install by the heater: https://smile.amazon.com/dp/B08R1HKZ78/ https://smile.amazon.com/dp/B08R1HKZ78/ or this: https://smile.amazon.com/gp/product/B09V7MDZHF https://smile.amazon.com/gp/product/B09V7MDZHF under the sink. There's a remote available also. By sure and carefully read the details - there is an "E" model, be sure and understand the difference and pick the right kind for your setup.
- bluSCALE4 4y ago
  I have everything I need, I just need the position of the expansion tank confirmed.
  - ars 4y ago
    I'm kind of confused on the question since you said "expansion tank". Which I guess is used because of a check valve - but that's if you put a check valve to the cold water back to the city, which isn't really part of a recirculation installation. A check valve for the recirculation should not need an expansion tank. A heat pump water heater will not work well with this mixing valve - just pipe the hot water direct to where it's needed, don't mix it with cold. A heat pump doesn't really want to make very very hot water, unlike fuel heat. This valve is meant for you to heat the water extra extra hot, then mix it. It's used when you have a small tank, and a lot of usage. It wastes energy, but gives you more hot water. It's just a bad idea to mix with a heat pump which much prefers lower water temperature. And using this mixing valve with a recirculating pump can't possibly work. This valve adds cold water, but a recirculating valve circulates the same volume of water, and does not add any. There's simply no way that it can work - it's impossible. Do you get why? Are you planning on having the recirculating pump always on, or do you prefer to press a button and wait a short time for the hot water? I ask because if you prefer the first type, you really want a dedicated return pipe for it. The second type can use the existing cold water pipe for return, but even then works much better with a dedicated return. Without a dedicated return line you never have cold water, the cold water is always warm because when you turn on the cold water, some hot water flows via the pump, and to your faucet. The expansion tank should be connected directly to the hot output of the heater before any mixing valves or recirculating stuff.

deathanatos 4y ago

On a FIRST robot, we needed something similar. There's "full reverse", "full forward" and "I need fine control", and the original mapping of joystick to wheel motors was linear. It didn't work well for "fine control". We ended up with motor = joystick³ (or some other odd, greater than 1 power; it might have been ⁵). Then you fix, via coefficients, the endpoints of the equation such that the lowest joystick value hits the full-reverse motor setting, and vice versa for forward. The exponent dampens the curve near zero, so there's more "joystick space" spent on the very slow speeds for the fine control, but the operator can still ask for max speed if they want it. (With joysticks, you also have to deadzone the middle, as "operator has centered the joystick" will sometimes report joystick values of 1 or -1, instead of 0. Or buy a better joystick.) I'm not 100% sure I'd apply this to a shower: max hot on my shower is hot, I don't usually ever want it. And I wouldn't want to scald someone. For a long while, our shower was not the typical tiny goldilocks zone surrounded by ice and lava: … it never really got above "lukewarm", even at max. We had the shower valve replaced and it works better now. (And, apparently, as I learned, there's a mixing valve at the hot water heater: i.e., the hot to the shower is not direct from the water heater, like I had imagined. We raised the temp there, slightly.)

pc86 4y ago
When my wife and I met she lived in an apartment with an amazing shower. The pressure was good but the temperature was fantastic. I had never had an apartment shower with water that got so hot. I barely even went half-way on the knob before I was turning it down. I asked about it and her response was "oh yeah I complained to my dad and he looked at the heater, there was something on it that he broke off." Turns out there was some piece of plastic or something put on by the landlord to limit the top temperature of the water, so he took it off. It didn't keep the hot water from running out but when you had it, it was great.
waste_monk 4y ago
>(And, apparently, as I learned, there's a mixing valve at the hot water heater: i.e., the hot to the shower is not direct from the water heater, like I had imagined. We raised the temp there, slightly.) When we changed from instant hot water to water tank + heat pump, the guy said the tempering valve was a safety thing (IIRC ours was set to 60 degrees Celsius by default, but could go up or down about 10 degree either way). That is, if you accidentally step in the shower with only hot water on you'll still hurt yourself but the damage will be limited to "strong profanity and aloe vera" instead of "you've won a stay in the burn ward". Although saying this, I did a quick bit of research and found that 60 may still be too high [1]. I have an IR thermometer so I think I'll measure the temperature of my shower (after any loss from pipes etc.) and see if the tempering valve needs adjusting down. [1] mild nsfw - image of scalded foot https://whywait.com.au/a-serious-hot-water-burn-occurs-in-one-second/ https://whywait.com.au/a-serious-hot-water-burn-occurs-in-on...

yehudalouis 4y ago

Just add a gear affixed to the handle, and then a second gear mated with that, and find the gearing ratio that allows the granular/sensitive inputs you want.

russellbeattie 4y ago

The amount of water wasted waiting for the water to warm up must be astronomical. In my place it can take three or four minutes of the water running to get warm - if not longer - and I don't think that's atypical. Multiply this by 7 days a week by everyone who showers in California alone and it seems like an issue that should get some serious attention.

rconti 4y ago
It's particularly bad with my tankless hot water heater that apparently doesn't even turn on for 15 seconds, and then you wait for the hot water to get to the shower. I swear the whole thing takes 60-90 seconds, and I live in a tiny house. I can't fathom what the hot water is doing on its way to the faucet. (well, yeah, some of that time is also spent heating the cold uninsulated under-house pipes).
- 0x457 4y ago
  I swear I had to wait nearly 5 minutes every morning before _warm_ water starts coming out, and our tankless heater was a wall away from shower.

standardUser 4y ago

I'm obsessed with showers and also wonder why we are so spectacularly bad at making consistently good showerheads with consistently good pressure and temperature control. One issue the author overlooks is that we have minimal control over the temperature of the cold water, and this temperature fluctuates throughout the year (at least here in NY, not so much where I lived in SF). As a result, the range of the dial I use changes from summer to winter. There are hot parts of the dial I use everyday in the winter that would simply burn me if I used them in the summer. Temperature can even change during the course of the shower! I notice this mostly in the winter. I speculate this is due to the cold water in my building pipes being used up and then replaced by the truly cold water from underground. I once tried to shower with that icy water when the hot water went out (just before a big trip) and I managed to completely numb my lower body (I did not have the fortitude to try and shower my upper body too).

aidenn0 4y ago
The water pipes to my shower go through an exterior west-facing wall. Mornings in the winter, the first half-gallon or so of water is basically the same temperature as the outside air-temperature. Evenings in summer, the first half-gallon can be painfully hot, even from the cold-water supply.
culebron21 4y ago
We have central hot water, and in winter hot water is incredibly hot, because the thermo-power station runs high.

aliceryhl 4y ago

Our shower has two dials: temperature and pressure. The temperature dial has a specific temperature that it will "snap" to. (When increasing temperature, it will stop there unless you hold in a button. It doesn't snap when decreasing the temperature.) Generally, I find the temperature it snaps to quite pleasant, so I just put it at the snap temperature and then open for the water with the other dial.

farhanhubble 4y ago

Very interesting exploration. However does this assumption really hold for the commonly used valves: >Since temperature has a nearly >linear relationship with control >rotation I thought the valves have circular openings and the flow changes non linearly, which I have always experienced too. Just a few days back I was thinking of why no one has thought about linear controls.

jnellis 4y ago

I've noticed you don't see the pivot type valves anymore where you can just go up and over to hot right away. Most shower valves now are turn-throughs, where you start at cold and go up to hot. Having installed a few now, I think this has to do with the federal law for having a scald prevention device in the valves control (much like having a low-flo device in shower heads.) Both instances, they are plastic and so you can remove them or adjust them later. I think it's just easier to make a scald prevention device for a turn-through valve than a pivot valve and that's why most shower handles suck today. It's just a tiny plastic piece that impedes how far into the hot range the handle will go.

ars 4y ago

People should stop buying pressure-balance shower valves, and switch to thermostatic valves. My shower valve is actually marked in degrees on the dial, and you set it to exactly the temperature you want and then don't mess with it - it will adjust as hotter water arrives.

PebblesRox 4y ago

I was house-sitting one time and took several miserable showers before realizing that the temperature dial started out on hot and got colder the farther I turned it!

theboywho 4y ago

Thinking from first principes, what about a shower handle that copies how air conditioners and heating work, something like a screen showing the exact temperature of the water with an Up and Down buttons to control the temperature.

loandbehold 4y ago
These exist: https://www.build.com/digital-showers/c131744?facets=application_s:Digital%20Shower%20Controls https://www.build.com/digital-showers/c131744?facets=applica...

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hbarka 4y ago

I loved the seriousness of this manifesto. A most-pressing issue indeed. The search for the better shower handle will be squabbled just like the quest for a better mousetrap. My two cents—a cam in the shower handle could follow that curve.

dclowd9901 4y ago

Just bought a Grohe thermostatic shower control and it’s one of the best things I’ve ever bought. Saves water and keeps the temperature comfortable. Highly recommend a thermostatic control.

culebron21 4y ago
I saw these in Germany and bought one for my home when I got fed up of adjusting the shower at home. I told my parents, -- they'd have the same problem, and one would shuffle the toilet while the other was taking shower -- but they didn't bother, until I just bought and installed one for them as a gift.

whatyearisit 4y ago

I've focused on this problem for some time too. The ultimate solution was to buy a color changing shower head from LIDL. This made it so easy to always be in the right temperature zone when taking a shower. The shower head has lighting that turns to green when the temperature is between 34-38C°. It's red when the temperature is above 38°, and turns to blue when it's below 34°C. It also shows the current temperature as a display which you can see while you are under the shower. The sensor setup also seems to be powered by the stream that flows through the shower head and only turns on when water is running. I hope this helps.

cirrus3 4y ago

Why is there no mention of the water heater temp control? If the water is way too hot on one end, you need to calibrate your input before worrying about the control of the output.

afinlayson 4y ago

This is one of many problems with the lack of innovation in the home in the last 40 years. Being a former IOT UXE I've been fascinated with this space. It's too bad my pitches never took off.

midoridensha 4y ago
There's no lack of innovation in the home. It's just that Americans refuse to adopt any of the innovations that have become commonplace in the last 40 years.

rconti 4y ago

2 side-rants: * Physical shower controls themselves. The typical US single-handle shower control is awful. Maybe I'm stupid, but it's never intuitive to me which side is hot and which side is cold. Much of the time the handle is pointing down, so you have to visualize an arrow extending through the top of the control, pointing left (hot) when the handle is on the bottom right. Sometimes they point entirely different directions, or the rotational positions of off, cold, hot make no sense at all. As I write this, it occurs to me that it's probably obvious that cold is always closest to "off", and "full on" is always full hot, but I'm over 40 and this has never occurred to me until now, so it can't be just me. Anyway, for whatever reason, when they're not labeled, i've never been able to 'remember' which side is hot and which side is cold. Again, maybe it's just me, but I've never had any other such dyslexic tendencies outside of faucet control. I think in my head "C" is on the left because it places C and H in alphabetical order? * Tankless hot water heaters. I want to like them. I've had them in my last 2 houses, covering the past 12 years. I can't imagine buying a water heater with a tank, but... The (central) tankless heaters take 15 seconds to turn on, and the water takes forever to make its way across my tiny house. So much water and time is wasted. And they shut off after some minimum flow rate. So if you try to use 'too little' hot mix (hot water heater set 'too high' or cold water input too warm, say, in the summer), the water heater decides to click off.. which you only notice 20 seconds later as the hot water trickles out of the pipes, and now you have to wash, rinse, repeat the whole awful cycle of turning the handle to full hot, waiting for hot water again, turning it down, but hoping you didn't turn it down too far. I've turned the hot water heater down as low as it'll go without much noticeable difference in this behavior in either house. Perhaps because the minimum flow rate actually depends on the setpoint of the hot water, which would make sense. It's worse in the summer. It's only a problem I have in 10% of my showers, but it drives me nuts.

bschwindHN 4y ago

I've been enjoying my digitally controlled shower temperature for years now. Japan figured this out a long time ago. I know the the temperature I like for a given season, and have up/down buttons to adjust it if needed.

jameshart 4y ago

Much of the confusion in this thread comes down to the fact that in the US, the standard shower valve is a 'pressure-balanced' valve, which allows you to select a flow-ratio between hot and cold feeds, but does not in itself maintain any particular temperature - it just ensures that in the event of pressure changes on one or other feed, the overall mix is maintained (preventing temperature spikes if someone flushes a toilet). Whereas in many other parts of the world, the standard shower valve is a 'thermostatic mixing valve', which allows you to select a temperature, and balances the inputs to achieve that desired temperature mark. Note that if you go to, say, HomeDepot.com, and look at shower faucets, you will not find thermostatic mixing valves. Only pressure balanced. The only thermostatic component in conventional american shower valves is an anti-scald-cutoff. Thermostatic valves do exist, but they're not the ones that are bundled into showers and that therefore get employed by the average landlord who is grabbing the cheap standard parts off the shelf. Thermostatic is a premium option, and not one that even crops up in the search result filters for showers. So most Americans have simply no idea that thermostatic valves are a thing. Whereas if you go to, say, diy.com (which is the store of B&Q, an equivalent store in the UK), and look up showers, you will find all the basic 'mixer showers' have thermostatic valves.

saghm 4y ago
> So most Americans have simply no idea that thermostatic valves are a thing. Having very limited travel experience outside the US, my mental model of what the temperature control on showers was supposed to be doing was thermostatic, and I just assumed that they were just bad at it. You may have just explained one of my longest running minor peeves, which is that I've always found it basically impossible to maintain a shower temperature I find comfortable without needing to make adjustments. Given that I don't own my home at this time, I probably can't do anything about it any time soon, but at least from now on when I have to deal with the fluctuations in temperature I'll know that I'm not crazy and this is actually expected behavior.
- account42 4y ago
  It gets even worse when the water heating is flow activated (switching between 0 and 100%) and your faucet/shower head is too gunked up to allow for enough flow from at the desired hot/cold mix.

deleted 4y ago

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mlnhd 4y ago

I want a valve that turns off the hot water supply completely after 10 minutes

ab8 4y ago

I want to be able to control flow and temperature separately.

throwaway892238 4y ago

There is a special kind of engineering that goes into luxury cars to get the windows to make a pleasing sound when you roll them up. That's the kind of engineering it takes to make a shower that only produces comfortable temperature water.

culebron21 4y ago

Thermostatic shower mixer by Grohe and some more manufacturers fixes this problem, and also 1) when someone shuffles the toilet on the same pipe, 2) when you use hot water from a heating tank on the cold pipe. https://duckduckgo.com/?t=ffab&q=grohe+thermostatic+shower&ia=web https://duckduckgo.com/?t=ffab&q=grohe+thermostatic+shower&i...