Hey plumbers! Instant hot water at kitchen sink.

DutchmenSport the system I saw was by convection as stated. There was no pump. His hot water heater was in the basement and there was two trunk lines one from the top of the heater and one to the bottom. It worked.

ScottG, Nope there was a return line to the bottom of the hot water heater where the drain is.

I helped install a system like that with my brother-in-law when he owned a laundry mat so the machines would have instant hot water. (this was many-many years ago). The principle is to put a return back to the water heater inlet from the end of the hot water line. The water is then in constant motion with a circulating pump.

Yes, you can do this, but you'll have to have a dedicated pump, either battery or AC. Most likely battery, like your on-board water pump. Then the water will constantly circulate, and your water heater will run a lot more. That's not so bad if your on electric, but if you're on propane, your water heater will eat that up much quicker.

So, you need to make a continuous loop between your hot water pipe at the sink and the inlet at the water heater, and install a circulating pump.

It can be done, but if your water heater is THAT close to your sink, why? Having that pump run 24x7 would drive me nuts!

IF I understand the system your talking about, it requires a pump to circulate the hot water either continuously or it involves a switch that turns on the pump just before you need the hot water.