hot water on Demand

[ITD]

Originally Posted by jeffk

An instant heater doesn't fire until you start drawing water anyway. A recirc system keeps the water in the delivery pipes hot so you don't have to wait for it to get from the heater to where you are using it. However, pumping hot water around the pipes full time is going to waste heat to keep the pipe water hot, even while you are sleeping and not using water.

As to a push button recirc system, if it hasn't been running, it is still going to take some time to heat the water in the pipes, probably just about as long as if you just turned on the faucet. The only advantage would be that you wouldn't be wasting water down the drain while it heated up. You could push the button, do something else for a minute or so, then turn the water on.

I don't know a lot about these heaters but I thought the selling point was tankless instant hot water, maybe not. A circulator would get hot water through the pipe much quicker than a low flow faucet.

I just checked out the Rinnai site and they have a heater with a built in recirc pipe, to keep the water in the pipe hot.