Hot water recirculating pump

[Alan24601]

Keeping the fresh water tank full and minimizing the amount in the grey tank is my goal. I will make an attempt to install a Watts valve and see if it works without an additional pump. I suspect I will need the recirculating pump to get the most benefit. The grey tank seems to be the limiting factor when dry camping. This trip I had to drain some gallons to comfortably make the duration.

[CampDaven]

Originally Posted by JFXG

I put a system like that in my boat some years ago, with paralleled manual switches in the head and at the galley sink. IIRC I had to run the pump about ten seconds to get hot water. Worked great.

I get hot water in about 10 seconds or less now, without the recirc gizmo.
I think it would be really nifty to see charts of the daily hot water requirement event count against the hot water arrival times between no recirc and with recirc, and the volume savings for supply and grey tank.
My guess is that the difference would be negligible.

Okay, got charts? ;-)
I dont really care, but am curious.

[KIX]

Several years ago a friend addressed this issue by installing an electric sprinkler system valve energized by a momentary switch. The valve passed water from the hot water line at his shower back to the fresh water tank. He used something like 1/4" line and said it would take about 45 seconds to get hot water at the shower head.
I had always thought those valves required 24v to operate but it worked for him.

[Ray,IN]

Originally Posted by KIX

Several years ago a friend addressed this issue by installing an electric sprinkler system valve energized by a momentary switch. The valve passed water from the hot water line at his shower back to the fresh water tank. He used something like 1/4" line and said it would take about 45 seconds to get hot water at the shower head.
I had always thought those valves required 24v to operate but it worked for him.

I've read several posts at escapees.com from full-timers who boondock a lot use a very similar setup. One of them even installed timers-push the button and the timer shuts it off when hot water arrives at the valve for that faucet; based on previous time tests.

[BrutusTheDog]

I have spent a lot of time thinking about adding the following to my TT as we boondock a lot.

Parts:
2 - Normally Closed, 12V solenoid valves (potable water and temp rated)
1 - Normally Open, 12V solenoid valve (potable water and temp rated)
1 - 12V Timer Relay (pulse activated) with at least 2 relays
1 - Push button (perhaps with LED)
Assorted pipe fittings
Assorted electrical connectors and wire

Install 1 NC valve under sink (between hot and cold supply) at furthest point from Water Heater. (In my case the kitchen sink)
Install 1 NC valve at water pump between water tank and pump inlet.
Install 1 NO valve in cold water line after the pump and after the line "Ts" off to supply the water heater. (This ones tricky to explain. You want to be able to interrupt the flow through the cold side, but still allow cold supply to water heater when the system is activated)
Install push button in convenient spot (you could install several in parallel such as kitchen and bath)
Wire in Timer Relay to sent current to all 3 Valves and to water pump.

Are you guys still with me?

The system when activated uses the existing cold supply lines as a return path for the hot side.
The pump will come on and draw water from cold supply line and pump it to the Water Heater forcing hot water through the valve (now open) at the kitchen sink.
The timer is adjusted for how ever long it takes currently to get hot water to the sink from a cold start.
One of the nice things is you only have to run wire and not water lines.

With a little more thought and modification you could use it to heat (carefully) your water tank in the winter.

All comments and critiques welcome.

Loulong, what did you use to draw your diagram?

[KIX]

Why not pipe return back to FW tank. That way you don't need a pump. Your Way would require a pump to overcome supply water pressure

[BrutusTheDog]

Originally Posted by BrutusTheDog

EDITS IN RED
I have spent a lot of time thinking about adding the following to my TT as we boondock a lot.

Parts:
2 - Normally Closed, 12V solenoid valves (potable water and temp rated)
2 - Normally Open, 12V solenoid valve (potable water and temp rated)
1 - 12V Timer Relay (pulse activated) with at least 2 relays
1 - Push button (perhaps with LED)
Assorted pipe fittings
Assorted electrical connectors and wire

Install 1 NC valve under sink (between hot and cold supply) at furthest point from Water Heater. (In my case the kitchen sink)
Install 1 NC valve at water pump between water tank and pump inlet.
Install 1 NO valve in cold water line after the pump and after the line "Ts" off to supply the water heater. (This ones tricky to explain. You want to be able to interrupt the flow through the cold side, but still allow cold supply to water heater when the system is activated)
Install 1 NO valve between water tank and pump.
Install push button in convenient spot (you could install several in parallel such as kitchen and bath)
Wire in Timer Relay to sent current to all 3 Valves and to water pump.

Are you guys still with me?

The system when activated uses the existing cold supply lines as a return path for the hot side.
The pump will come on and draw water from cold supply line and pump it to the Water Heater forcing hot water through the valve (now open) at the kitchen sink.
The timer is adjusted for how ever long it takes currently to get hot water to the sink from a cold start.
One of the nice things is you only have to run wire and not water lines.

With a little more thought and modification you could use it to heat (carefully) your water tank in the winter.

All comments and critiques welcome.

Loulong, what did you use to draw your diagram?

I finally got some diagrams made. Lets see if I can successfully post them.
https://picasaweb.google.com/lh/phot...eat=directlink

https://picasaweb.google.com/lh/phot...eat=directlink

The only thing I see that may be problematic is that because of the internal pressure switch in the pump,there may not be enough pressure drop to kick on the pump. You may be able to fix that by somehow delaying the closing of the NO valve at the water tank. Have to think about it and research parts.

All comments and critiques welcome.

[Old Bounder]

Originally Posted by BrutusTheDog

I finally got some diagrams made. Lets see if I can successfully post them.
https://picasaweb.google.com/lh/phot...eat=directlink

https://picasaweb.google.com/lh/phot...eat=directlink

The only thing I see that may be problematic is that because of the internal pressure switch in the pump,there may not be enough pressure drop to kick on the pump. You may be able to fix that by somehow delaying the closing of the NO valve at the water tank. Have to think about it and research parts.

All comments and critiques welcome.

A quick opening of the tap should overcome that pressure and allow the circulation to start.

[deandec]

Originally Posted by Alan24601

Keeping the fresh water tank full and minimizing the amount in the grey tank is my goal. I will make an attempt to install a Watts valve and see if it works without an additional pump. I suspect I will need the recirculating pump to get the most benefit. The grey tank seems to be the limiting factor when dry camping. This trip I had to drain some gallons to comfortably make the duration.

Just installed the Watts system at home.

If the pump is not working, hot water does not appear at the faucet on any improved basis in our house. I know, because the GFI in my garage shut off the Watts pump.

[Keyair]

Reviving this older, but interesting thread.
Can any of the original posters update?

[4x4van]

Someone here, I believe in the Class C section, recently installed a 12v valve in a return line from his hot line (at the faucet) back to the fresh water tank. He only needed to hit the switch (opening the valve), let the water circulate for about 10 seconds, then hit the switch again to close the valve. Now there was hot water at the faucet, without wasting a single drop.

I am getting ready to do the same thing to my class A; I have already purchased the valve. In my case, there is 41.5 feet of line from the water heater to my kitchen faucet. Calculated out with a 1/2" line, that means that I waste 1.7 gallons of water before I ever see a drop of hot water at the faucet, every time. Sorry, but that is unacceptable for boondocking.

Edit: Found the link: http://www.irv2.com/forums/f101/how-...ge-318037.html

[Kiawah]

You don't want to use the cold water line as a return, because that water in the cold water line will be hot.....so when you turn the cold water on at the faucet it will initially come out hot.

Opening a valve which then dumps into the fresh water tank works whether you're on shorewater or tankwater, great idea and very simple, and you don't need another pump.

[Keyair]

Good info!
I am seriously looking at adding a solar hot water system to my rig... Here in CA, with an Airstream, heat is not hard to come by!
I am in the process of replumbing the whole unit with PEX anyway, and plan to insulate both hot and cold just in case we go somewhere cold.
If I added a return line from the kitchen(end of the run), and add a solar powered pump, it would circulate the hot water thru the pipes, up into the collector, back into the system, in theory it would heat the whole system.
I would install drain and bypass valves to the solar part in case of freezing temps.
Anyone care to comment or advise, feel free!

[gatorcq]

I had a used 12v pump. using faucet hoses and shark bite valves. Installed it under bathroom sink.
2 valve, 4 hoses, 2 add-a-tee and 1 pump.
Turn it on, wait 1 minute, very hot water.

Pumps water from the hot line back into the cold line. Works great.