Foretravel Owner's Forum For owners and Fans of Foretravel Motorcoaches April 25, 2024 ...

Hot Water Recirculation

I did not want to run cold water down the drain while waiting for hot water.  It would take 30 seconds or more to get hot water.  So I found an electronic timer/relay, a solenoid valve and a bunch of plumbing fittings and went at it.

Parts List
Timer/relay controller
12v 3/4" Solenoid Valve
2-3/4" pipe couplers
2-3/4" male pipe to barbed fittings to fit your flexible tubing.
1/2" pipe coupler to attach to the hot side of the water manifold. The spot opposite the toilet is usually open
  If there are no unused spots you have to T into a PEX hot line.
6 ft of tubing.  I used 5/8" to match up with the barbed fitting the hardware store had that day.
1/2" spin weld tank fitting to glue to the water tank
Adhesive for the 1/2" spin weld fitting
1/2" hose pipe to barbed fitting to fit your flexible tubing.
4 hose clamps
Teflon plumbing tape
Wire ties.

12v on/off switch
12v momentary contact switch

This is the timer/relay circuit I used.
Directed Electronics Inc 528T 12v Accessory Pulse Timer

Amazon.com : Directed Electronics Inc 528T 12v Accessory Pulse Timer :...

And the solenoid valve.  You might be able to find a 1/2" one.
12V Solenoid Valve - 3/4"

12V Solenoid Valve - 3/4": Industrial Solenoid Valves: Amazon.com: Industrial...

At each end of the valve you will need a pipe couple and a barbed fitting of the appropriate size for the tubing you are using.

Attaching a fitting to the low density polyethylene water tank is not easy.  You cannot use regular solvent glues.  The following fitting works well with the 3M adhesive meant for this type of plastics.  A barbed fitting for the tubing size you are using is needed here.

Ameri-Kart (53) 0.5" Female Pipe Fitting

Amazon.com: Ameri-Kart (53) 0.5" Female Pipe Fitting: Automotive

3M 4693H Clear Scotch-Weld High Performance Industrial Plastic Adhesive, 5 Ounce

3M 4693H Clear Scotch-Weld High Performance Industrial Plastic Adhesive, 5...

This is an alternate (and less expensive) way to connect a 1/2" pipe to your tank.  The Uniseal fittings are a rubber grommet that fits in a hole you drill in the tank and then you slide the pipe through hole in the grommet.  It makes a tight fit with some give for movement.  They come in different sizes.  I have a larger one to use when I put in a gravity/fast fill port.

1/2'' UNISEAL Flexible Tank Adapter (bulkhead)

1/2'' UNISEAL Flexible Tank Adapter (bulkhead): Pet Care Products: Amazon.com...

The flexible tubing is much easier to run than PEX.  There is not a lot of room around the manifold and PEX is pretty stiff. 

From the hot side of the manifold run the flex line to the top of the bay where it connects to the solenoid valve.  From the solenoid valve run the flex line to the fresh water tank connection which is slightly lower than the solenoid valve.

I mounted the timer inside the kitchen cabinets so that I could adjust timing if needed.  The on/off switch and the momentary switch are mounted on the kitchen cabinet face just under the cooktop.

I have the timer set for 20 seconds.  When the momentary switch is pushed the solenoid valve is opened for 20 seconds. Cold water is pumped to the hot water heater tank, hot water comes back towards the manifold, the water between the hot water tank and the manifold that has cooled off is returned to the fresh water tank.  After 20 seconds the solenoid valve closes and there is hot water at the manifold.  Now there is only 5-10 seconds of cold hot water between the manifold and the kitchen, bathroom or shower.

I thought about using a "T" in the shower hot water line close to the shower valve which would have gotten the hot water to the manifold and to the shower valve but the plumbing runs seemed much more difficult.  The bathroom sink and the kitchen are the most commonly used fixtures.  A "T" in the kitchen hot water line would work but that involves crawling under the sink to do plumbing and a potential leak.  So the manifold was a good choice.

While doing all of this I removed the panel in front of the fresh water tank, cut it into three pieces and added some hinges and a latch.  Now I can just open the door to see how much water is in the fresh tank and store a few more things behind the panel.

Roger

In an effort to save water when extended dry camping in Quartzsite, I found this old thread. 

I looked at the RV Aquaview product, but did not want to drill holes in the Corian in the shower, and the thought that having a blue plastic rod with black PVC pipe in the shower just seemed too Winnebago to me.  So, I followed Roger's methodology here and plunged into the project and got-er-done.

I used this 12V water valve off Amazon (looks just like the icemaker valve on my fridge) (2 for $10...just in case since they're Chinee), Amazon.com: Ximimark 2Pcs 1/2" Thread Plastic Electric Solenoid Valve Water...

and this made in the USA timer:  Small Miniature time on off cycling delay relay 0.1 sec to 9999 hours. 5V... and programming buttons.  Online instructions on how to set it.

I wired the power for the timer/valve to the vanity make up light switch, and as a trigger, installed a momentary on push button switch right next to that below the sink.

I plumbed the system by gaining access to the rear of the shower thru panels in the make up corner cabinet in the bedroom, installed a sharkbite T fitting and several 90's right at the hot water inlet to the shower valve, and ran 1/2" PEX under the rear of the shower, behind the toilet, to under the sink area, where I installed the valve and timer under the left sink drawer, just above the fresh tank fill point and ran the PEX down to the wet bay on the driver's side (total of about 8' of PEX).  Had to pick out a ton of silicone and then resealed it all afterwards.  Ran the hot water return down into the wet bay and connected it with a sharkbite T and some adapters into the fast fill set up I'd put in last year.  Added a check valve in place of the manual on/off valve I had in there for the fast fill.  See picture.

I programmed the timer with program #14, "single shot" and set the timer to 25 seconds and that gets warm water to the shower....enough to wet my hair when I jump in.  On cold days, I'll just hit the trigger button twice.  It's gonna save me a lot of water...guessing a 1/4 to 1/3 tank.

Man I love this forum.  Thanks again for all the advice here.  Woody