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Comment by snypher | Hacker News Reader

I have seen a return loop on the hot side, but not returning through the cold side. Do you have more info on this? (I do wonder if recirculating hot through a pipe next to a cold pipe would result in heating the cold)

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The thing consists of a) a pump that goes on the output of the water heater, and b) wax-based valves that go between the hot and the cold under each sink where you want hot water without having to wait a long time. The valves turn on when the water on the hot side cools, and they close when it gets hot. The pump stops when the valves and hot faucets are all closed, and it has a timer for scheduling hours of operation. I believe it's this:

  https://aurorixs.shop/product/watts-500800-instant-water-recirculating-pump-system-with-built-in-timer

That sounds like a great way to get Legionnaire's, unless I'm missing something.

I've been doing it for 15 years. No legionella here.

I think all apartment buildings have recirculators so somehow it works.

actually its quite the opposite. because the hot water is constantly recirculating its hard for the bacteria to grow. Kind of like why they say never drink from stagnant water but water that is flowing is safer (not neccessarily safe to be clear)

So you’re always pumping hot water through your pipes? Does that not end up wasting quite a bit of energy? I guess in winter it’s not a big problem since you’re heating your house anyway, but presumably in summer it is just adding unwanted heat?

In the winter, as you note, it's not much of a waste, and it helps keep the pipes from freezing.

In the summer... this is central Texas, so the sun helps keep the water in the pipes hot, so I imagine that the pump is on less often than in the winter. I've not checked though. My gas bills are not out of the ordinary, so I think it's not a ridiculous waste.

4 day old post but these can have timers so they only run for one time window such as when you wake up.

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