I've seen in homes a system that provides hot water circulation via convection from the hot water heater to the various faucets and back that allows instant hot water. How would I do this for my kitchen faucet? My hot water heater is in the compartment right next to the faucet.-Jeff

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.

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!

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

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.

The way to do this is:1. run a line from the hot water feed at the faucet to the cold water intake on the hot water heater.2. put a one way flapper valve in this return line so the open side feeds the cold water inlet connection.How it works: Hot water goes to the faucet and sits there. As it cools it sinks thru the flapper valve an to the cold water feed line of the hot water heater. The flapper prevents cold water from going up to the hot water faucet. It works very well in a home situation by convection cooling but not sure how it would work in an RV.

Hey plumbers! Instant hot water at kitchen sink.

24 Replies

BurbMan
Explorer II
Mar 21, 2014
gmctoyman wrote:
I did mine mainly for boondocking. Tee into hot water line at galley wit a 1/4" line to the inlet side of the water pump. In that line put a 12v selanoid valve. Control that valve with a remote control on/off switch with 2 remotes, one in the bathroom, one in the galley. Push the button and circulate water from the water heater, back to the tank/pump inlet, count to 20 and water is hot. It can be used on city supply but need to make sure you don't forget that it's on, it will over fill the water tank.

This is what I was thinking. Our WH is at the rear of the TT so the shower is fine but you waste 1/2 gal or so at the kitchen faucet waiting for hot water. If I teed into both hot and cold at the kitchen faucet and connected those lines with a bypass line that had both the solenoid valve and a separate pump with an intermittent contact switch (press and hold for "on").

So pressing the button would open the bypass solenoid and turn the pump on at the same time circulating water from the hot feed at the faucet back through the cold line. Hold button for 20 seconds then release, no danger of leaving it on.

Energy usage would be the same, cold water is still entering the HW heater to replace the hot you are using, the only difference would be that the cold water is coming from what is sitting in the HW line not from the tank. Benefit would be water savings when boondocking with no extra energy cost.

Thoughts?
C_Schomer
Explorer
Mar 20, 2014
It would work just like old convection hot water space heat and convection radiators and the lines need to be big and have a lot of pitch. Craig
Unyalli
Explorer
Mar 20, 2014
Leaf-peeper dang nice install.
ependydad
Explorer
Mar 20, 2014
Unyalli wrote:
ependydad wrote:
IMO, it sounds like what you win in water usage, you lose in power usage.

You have my curiosity. How would you loose in power usage?

For a power usage, I was going off of the idea that there would need to a pump integrated into this solution. However, reading further posts- I'm not positive if this is the case or not. But it's what I was saying- less hot water, more electric used to run a pump. I think the extra heating of water seems like it would be nominal especially if the lines are insulated in this loop.

Unyalli wrote:
ependydad wrote:
Why not look at a dedicated instant hot water faucet?

What are we talking about? Again, curious.

As for a dedicated instant hot water faucet. My in-laws have one that they use to make tea and coffee. Here's one of many (and many at different price points):
InSinkErator Chrome Hot Water Dispenser

The more that I read, this doesn't seem to be what you want. From what I gather, you just want the hot water to be at the top, not super hot water for other purposes.
Leaf-Peeper
Explorer
Mar 20, 2014
Here's some photos of our Hot Water Recirculation system >> Here <<
motorcycle_jack
Explorer II
Mar 20, 2014
Unyalli wrote:

Ok, so looking at the picture of my hot water heater plumbing I would install a T in the incoming blue line at the bottom left. Then install a T in the hot water line up near the faucet. Now run a new line between these T's with a one way valve allowing the hot side access to the cold side. Yes?

Yup, you got it. The water in the tank is heated and rises in the feed line and as it cools it falls to the intake port of the hot water heater SO you have hot water at the faucet all the time. You might want to insulate the hot line to the faucet.
Unyalli
Explorer
Mar 20, 2014
The circulation loop would be the hot line to the faucet then back through a new line to the cold intake of the heater. Insulated this loop would be an extension of the tank and only feed cold into the tank till the loop has hot. I understand this would cause the heater to run a little more but don't believe it would be all that noticeable.
Bobbo
Explorer III
Mar 20, 2014
Unyalli wrote:
ependydad wrote:
IMO, it sounds like what you win in water usage, you lose in power usage.

You have my curiosity. How would you loose in power usage?

You are constantly pulling hot water out of the water heater and replacing it with cold water, cooling the tank, causing the heater to cut on more frequently, using either electricity, or propane more rapidly.
Unyalli
Explorer
Mar 20, 2014
ependydad wrote:
IMO, it sounds like what you win in water usage, you lose in power usage.

You have my curiosity. How would you loose in power usage?

ependydad wrote:
Why not look at a dedicated instant hot water faucet?

What are we talking about? Again, curious.
ependydad
Explorer
Mar 20, 2014
IMO, it sounds like what you win in water usage, you lose in power usage.

Why not look at a dedicated instant hot water faucet?