Why is it not used again and wouldn’t it be very efficient to combine with a heat pump for reuse?
Especially since water from shower or sink isn’t usually very dirty, couldn’t it be stored for a while in an isolated tank so that e.g. a heat pump can run more efficient on it than on usually colder air or colder ground water?
In: Engineering
It’s warm, but it’s not hot enough to provide much useful energy. Hot water/steam heat is much hotter than you’d be comfortable taking a shower in.
You’d need a whole separate drainage and pump system that’s only gonna run for a few minutes a day to recover the minuscule heat from lukewarm water flushed down the bath tub. Not worth the cost, and probably costs more energy to manufacture than you’d ever recover.
Sometimes the water that goes down those drains *is* very dirty too, so you’d need some way to select recycle or sewer.
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