I've also seen a system that used a pump and a thermostatic valve,
plus a control circuit. Before you turn on the hot water you press a
switch that pumps water from the (now cold) hot water line into the
cold water line via the thermostatic valve. Once the hot water gets
to the valve it shuts off and turns off the pump. Open the faucet and
you have "instant" hot water.
The pump doesn't have to pump against a large head pressure. the hot
and cold lines should have very close to the same pressure in them.
The bigger the pump capacity the faster you get hot water.
I saw this set up at a home show about 10 years ago. I don't know it
is still in production.
> Any problem with tapping off the hot water in the house?
> You can run it directly off and just wait for the hot water to get to
> the spigot when needed. If it's not a far run, this will work just fine.
> You can also use a little recirculator on the hot water line to keep hot
> water in the line, instantly available at all times. This is something
> that's quite nice in the house as well. Some friends of ours have this
> on their house, and the water is hot instantly at all times. It's
> really quite addictive.
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