Why is hot waste water (shower, sink…) not reused for heating?

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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

27 Answers

Anonymous 0 Comments

Practicality.

Not all water that goes down the drain is hot. Even when washing hands, or taking a shower, the water is usually “warm”. It would be unlikely that you could extract any meaningful amount of usable energy from it.

Hot water usage in the home is typically used only briefly. There would unlikely be sufficient quantity of hot water available for energy recovery.

And while most hot water sent down the drain doesn’t immediately appear to”dirty”, that’s not necessarily true for everything sent down the drain. This would require more maintenance and upkeep if you’re storing this in a tank for energy extraction later.

I imagine it would be far more practical, economical, and efficient to slap a small solar panel on a heating element and stick it in a tank of water or solution to keep it warm/hot.

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