3 ms·

The diagram shown in the article doesn't make a whole lot of sense to me. They've got the output of the heat exchanger going directly to the supply of the show

The diagram shown in the article doesn't make a whole lot of sense to me. They've got the output of the heat exchanger going directly to the supply of the shower where it mixes with the output of the water heater. This actually reduces the temperature of the shower and, as phugoid already noted, introduces undesirable temperature transients. It seems to me that it makes more sense to use the heat exchanger to preheat the feed to the water heater. This has the added advantage of making the energy exchange mechanism generally applicable to any hot water that exits via the drain which supplies the heat exchanger, not just shower water. Also, when you finish your shower and shut off the water, there is still heat in the drain and still water refilling the water heater, but the design as shown does nothing productive with that energy. Of course, one would hope that the heat exchanger itself is made of highly corrosion-resistant material. It would be quite nasty to have a leaky drain introducing gray water into your potable water supply.

extension 18y ago
It only reduces the temperature of your shower if you would otherwise be standing under 100% hot water, which would literally be lethal with a typical hot water system (I'm guessing you don't have a typical hot water system?). It's more likely you are using a mix of, say, 70% hot, 30% cold. If you use this thingy to heat the cold water, you could get the same temperature with maybe 60%/40% mix, thus using less hot water and getting a cheaper and/or longer shower.
- blahblahblah 18y ago
  Perhaps most people have the thermostat on their water heater set higher than it really needs to be? On the other hand, as a bachelor, I concede that my hot water usage pattern is not the same as an average household with a family of 3 to 5 people. I typically do use 100% hot water for my showers. The only exception to this is if I run the dishwasher or the washing machine a few hours before taking a shower, which will result in 100% hot water being too hot.

extension 18y ago

It only reduces the temperature of your shower if you would otherwise be standing under 100% hot water, which would literally be lethal with a typical hot water system (I'm guessing you don't have a typical hot water system?). It's more likely you are using a mix of, say, 70% hot, 30% cold. If you use this thingy to heat the cold water, you could get the same temperature with maybe 60%/40% mix, thus using less hot water and getting a cheaper and/or longer shower.

blahblahblah 18y ago
Perhaps most people have the thermostat on their water heater set higher than it really needs to be? On the other hand, as a bachelor, I concede that my hot water usage pattern is not the same as an average household with a family of 3 to 5 people. I typically do use 100% hot water for my showers. The only exception to this is if I run the dishwasher or the washing machine a few hours before taking a shower, which will result in 100% hot water being too hot.