4 ms·

I was actually looking at heat recuperation systems for bathrooms recently and stumbled upon https://ecodrain.com/en/ https://ecodrain.com/en/ - if we hadn’t a

I was actually looking at heat recuperation systems for bathrooms recently and stumbled upon https://ecodrain.com/en/ https://ecodrain.com/en/ - if we hadn’t already remodeled our bathrooms I’d have loved to have installed this. For now we make do with a heat pump water heater which is very efficient.

afandian 4y ago
I wonder how different it would be to use an off the shelf heat exchanger, e.g. this one? https://www.ebay.co.uk/itm/263272702860 https://www.ebay.co.uk/itm/263272702860 You'd probably have to filter the shower water before sending it through, but beyond that I wonder how different the principle is. Maybe being easy to clean is a significant factor in drain showers.
- shellfishgene 4y ago
  There may also be problems with sanitation rules, only a minimum of water should sit in the pipes, and then ideally hot our cold but not luke warm.
  - afandian 4y ago
    Got a link (or explanation) for that temperature stipulation?
    - shellfishgene 4y ago
      Yes, as tempestn explained this is to prevent bacterial growth, especially Legionella. Otherwise this can be a problem in areas where tapwater is not chlorinated.
    - tempestn 4y ago
      Temperature window for bacterial growth. Above about 120F harmful bacteria commonly found in water won't proliferate, but will survive. As you get hotter from there, they're killed off increasingly rapidly. Above 135 or 140 or so they don't survive long. In cold water they won't die off but also won't multiply quickly. The dangerous range is in the middle.
- twic 4y ago
  I think doing adequate filtration of the full waste water flow without losing most of the heat would be a challenge. And remember you're also sending soap suds down the pipe, which will pass the filter and leave deposits inside the exchanger. Also, if you're just using gravity to push the waste water through, what flow rate would you get on one of those units, and how many would you need to handle the full flow? The most persuasive waste water heat exchangers i've seen are based around the a large-diameter pipe, with conical sections connecting it to the input and output, where the waste water flows down the inner wall of the pipe in a thin layer, and the cold water flows up the outside. It's not as space-efficient as a conventional heat exchanger, but it avoids the problem of blockage. That would also be fairly easy to improvise, i think, given that you can buy copper pipe, or even buy copper foil and wrap it into a large, thin-walled cylinder.
twic 4y ago
There are numerous manufacturers of these things, eg: https://powerpipehr.co.uk/ https://powerpipehr.co.uk/ https://showersave.com/vertical-wwhrs/ https://showersave.com/vertical-wwhrs/ https://recoupwwhrs.co.uk/ https://recoupwwhrs.co.uk/ Ultimately they're just cleverly arranged copper pipes, so the barrier to entry for new manufacturers is low! I am keen to get one - my shower sits directly above a cupboard on the floor below, where it would be simplicity itself to fit. This article suggests the energy savings are not particularly big: https://www.thegreenage.co.uk/tech/waste-water-heat-recovery-systems/ https://www.thegreenage.co.uk/tech/waste-water-heat-recovery... ... but there are several comments reporting the opposite!
- ip26 4y ago
  It depends heavily on how much your house showers, what the water temperature is at the inlet to the house, and how ideal your plumbing is. The efficiency is highest with a vertical unit at least five feet in length, and that’s really just down to your house’s layout.
- hedora 4y ago
  Note the manufacturer of the GP's device claims a 33% energy savings. You can get a hybrid heat pump hot water heater with a coefficient of power of 4, for a 75% savings. If your water heater is in a garage, it is likely a simple retrofit. (If it is in a small closet, it will require a duct). Ignoring installation, the heat pump water heater costs more than those devices. With installation, I imagine it is cheaper.
  - hkt 4y ago
    Given the coefficient of performance of heat pumps is a function of the difference in temperature between the two mediums, if you can use heat recovery on the shower water you can boost your COP further by having both. I'm in the midst of this exact system being installed: it'll be extracting hot, humid air from the bathroom and receiving pre-heated mains water via a reclamation unit. The main thing with EAHPs is finding a plumber who is cognitively flexible enough to fit one. I'm on number six and it is finally going in next week.
fomine3 4y ago
Newer heat pump bath system in Japan supports to reclaim the bath water heat into heat pump bath system's tank. Though it won't reclaim from shower. https://www.mitsubishielectric.co.jp/home/ecocute/function/hot-return.html https://www.mitsubishielectric.co.jp/home/ecocute/function/h... https://kaden.watch.impress.co.jp/docs/news/523254.html https://kaden.watch.impress.co.jp/docs/news/523254.html
madaxe_again 4y ago
I just built an off-grid cabin, and built heat reclamation into our plumbing in multiple locations, as it seemed silly not to. Currently we’re using butane for our hot water, although I’m switching to biogas in the spring - the first stage of reclamation is a simple loop of hot water line around an insulated hutch in which the gas bottle lives - keeps it warm, as butane is useless in cold weather. The second stage of reclamation is exactly what he proposes - our cold water line comes in, spirals around the waste water line for about 5/40 meters of respective length, in an insulated sleeve, before hitting the boiler. Our input water is often barely above freezing - it’s the difference between having a cold/lukewarm shower and a scaldingly hot one.

afandian 4y ago

I wonder how different it would be to use an off the shelf heat exchanger, e.g. this one? https://www.ebay.co.uk/itm/263272702860 https://www.ebay.co.uk/itm/263272702860 You'd probably have to filter the shower water before sending it through, but beyond that I wonder how different the principle is. Maybe being easy to clean is a significant factor in drain showers.

shellfishgene 4y ago
There may also be problems with sanitation rules, only a minimum of water should sit in the pipes, and then ideally hot our cold but not luke warm.
- afandian 4y ago
  Got a link (or explanation) for that temperature stipulation?
  - shellfishgene 4y ago
    Yes, as tempestn explained this is to prevent bacterial growth, especially Legionella. Otherwise this can be a problem in areas where tapwater is not chlorinated.
  - tempestn 4y ago
    Temperature window for bacterial growth. Above about 120F harmful bacteria commonly found in water won't proliferate, but will survive. As you get hotter from there, they're killed off increasingly rapidly. Above 135 or 140 or so they don't survive long. In cold water they won't die off but also won't multiply quickly. The dangerous range is in the middle.
twic 4y ago
I think doing adequate filtration of the full waste water flow without losing most of the heat would be a challenge. And remember you're also sending soap suds down the pipe, which will pass the filter and leave deposits inside the exchanger. Also, if you're just using gravity to push the waste water through, what flow rate would you get on one of those units, and how many would you need to handle the full flow? The most persuasive waste water heat exchangers i've seen are based around the a large-diameter pipe, with conical sections connecting it to the input and output, where the waste water flows down the inner wall of the pipe in a thin layer, and the cold water flows up the outside. It's not as space-efficient as a conventional heat exchanger, but it avoids the problem of blockage. That would also be fairly easy to improvise, i think, given that you can buy copper pipe, or even buy copper foil and wrap it into a large, thin-walled cylinder.

twic 4y ago

There are numerous manufacturers of these things, eg: https://powerpipehr.co.uk/ https://powerpipehr.co.uk/ https://showersave.com/vertical-wwhrs/ https://showersave.com/vertical-wwhrs/ https://recoupwwhrs.co.uk/ https://recoupwwhrs.co.uk/ Ultimately they're just cleverly arranged copper pipes, so the barrier to entry for new manufacturers is low! I am keen to get one - my shower sits directly above a cupboard on the floor below, where it would be simplicity itself to fit. This article suggests the energy savings are not particularly big: https://www.thegreenage.co.uk/tech/waste-water-heat-recovery-systems/ https://www.thegreenage.co.uk/tech/waste-water-heat-recovery... ... but there are several comments reporting the opposite!

ip26 4y ago
It depends heavily on how much your house showers, what the water temperature is at the inlet to the house, and how ideal your plumbing is. The efficiency is highest with a vertical unit at least five feet in length, and that’s really just down to your house’s layout.
hedora 4y ago
Note the manufacturer of the GP's device claims a 33% energy savings. You can get a hybrid heat pump hot water heater with a coefficient of power of 4, for a 75% savings. If your water heater is in a garage, it is likely a simple retrofit. (If it is in a small closet, it will require a duct). Ignoring installation, the heat pump water heater costs more than those devices. With installation, I imagine it is cheaper.
- hkt 4y ago
  Given the coefficient of performance of heat pumps is a function of the difference in temperature between the two mediums, if you can use heat recovery on the shower water you can boost your COP further by having both. I'm in the midst of this exact system being installed: it'll be extracting hot, humid air from the bathroom and receiving pre-heated mains water via a reclamation unit. The main thing with EAHPs is finding a plumber who is cognitively flexible enough to fit one. I'm on number six and it is finally going in next week.

fomine3 4y ago

Newer heat pump bath system in Japan supports to reclaim the bath water heat into heat pump bath system's tank. Though it won't reclaim from shower. https://www.mitsubishielectric.co.jp/home/ecocute/function/hot-return.html https://www.mitsubishielectric.co.jp/home/ecocute/function/h... https://kaden.watch.impress.co.jp/docs/news/523254.html https://kaden.watch.impress.co.jp/docs/news/523254.html

madaxe_again 4y ago

I just built an off-grid cabin, and built heat reclamation into our plumbing in multiple locations, as it seemed silly not to. Currently we’re using butane for our hot water, although I’m switching to biogas in the spring - the first stage of reclamation is a simple loop of hot water line around an insulated hutch in which the gas bottle lives - keeps it warm, as butane is useless in cold weather. The second stage of reclamation is exactly what he proposes - our cold water line comes in, spirals around the waste water line for about 5/40 meters of respective length, in an insulated sleeve, before hitting the boiler. Our input water is often barely above freezing - it’s the difference between having a cold/lukewarm shower and a scaldingly hot one.