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Old 02-23-2019, 06:28 AM   #1
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Default Hot water diversion to fresh tank

Starting a new thread since I wasn't able to find a good thread on a hot water diversion line retrofit.

My house has a system that cycles hot water from the furthest tap back to the water heater so that I don't have to run the faucet a long time while waiting for hot water. It seems like that's a great idea for my campervan with the primary motivation of just saving fresh water that might otherwise go down the drain.

I'm thinking I'll install a diversion valve where the hot water line connects to my bathroom faucet (and maybe another on the kitchen sink) that will send water back to the fresh tank while I wait for the hot water to reach the faucet. Routing the return line would be pretty straight forward.

The challenge is locating this diversion valve somewhere where I can easily reach it without making big ugly holes in the wall. The faucet is a single lever with a pull out spout. A diversion valve designed to poke out of a sink hole would be perfect since I could cut a hole in the wall and seal around this valve.

Is thee already a thread on this idea around here somewhere? If not, any suggestions on a clever place to install the diversion valve? Or maybe there is just a better way to do this? Thanks.
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Old 02-23-2019, 07:04 AM   #2
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I used a solenoid valve for this purpose. It features a latching relay that holds the valve open and then lets it close when hot water is sensed up at the faucet. An easier method is to use a delay timer like this one: https://amzn.to/2U5jTqa Then just measure the time it takes for hot water to arrive and set the timer to slightly longer.

More info in our build thread on the Sprinter forum.

https://sprinter-source.com/forum/sh...&postcount=768

The valve was initially up by the kitchen faucet but I later moved it under the van right near the fresh tank. Our water heater is in the engine compartment so quite a bit of plumbing to purge until we get hot water. We use it all the time and works great. Definitely a huge water saver. Later post about moving the valve:

https://sprinter-source.com/forum/sh...&postcount=835

I need to add another return line at the back of the van where the bathroom shower and outside sprayer are located. This is another reason that I moved the valve to right near the tank. I'll just T into the existing return line from the kitchen to a point just ahead of the valve. I'll likely switch to a timer at that time because it will eliminate the need to sense the temperature. The line from valve to tank is only about 10". I used 1/4" ID hose for the plumbing.

Another use for this system is to use the water heater to keep lines and tank from freezing in cold weather. A cycle timer could be used to open the solenoid intermittently and run it for some length of time.

All the best,
Hein
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Old 02-23-2019, 07:13 AM   #3
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Very Clever! Much appreciated.

Did you really need the thermostatic controller? I'm thinking I could just push the button for a few seconds (while the water flows) and it would be fine.

In my case, if I err on the over purge side it's not a big deal since the Alde boiler keeps up well with the limited demand I put on it.
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Old 02-23-2019, 12:46 PM   #4
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We have a 'deck fill' from our boating past installed in the kitchen counter next to sink.

Normally we use it to fill our fresh water tank. That way we can fill the tank from any water source available - hose, hand pump, spring, bottled water, etc.

To save water while waiting for hot water to arrive at the faucet, the deck fill is positioned so we can swivel the faucet over the deck fill and simply run the water back into the fresh water tank until the water reaches the desired temperature.
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Old 02-23-2019, 01:03 PM   #5
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We also use a solenoid valve. As per Hein's "easier alternative", we have a pushbutton and a simple electronic timer that keeps the valve open long enough to purge the line of cold water. The timer simply keeps you from having to hold the button--you just tap it once. The diversion line simply runs back to a tee just upstream of the water pump.

valve.jpg
Timer2.jpg

Full report at Sprinter Source:

http://sprinter-source.com/forum/sho...ter#post398318
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Old 02-23-2019, 01:22 PM   #6
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It is standard for the shower in the Coachmen Galleria. See here:

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Old 02-23-2019, 02:49 PM   #7
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BTW: Note that there is no reason to go all the way back to the fresh tank. Teeing in anywhere upstream of the pump will suffice.
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Old 02-23-2019, 05:46 PM   #8
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Dutch: That was the exact design I had in mind on my first post! Thanks for the video link.

Avanti: I'm now planning to use your design with the solenoid just upstream of the pump. I've got easy access to that location and the wire runt to the switch will not be too long. I like the idea of having return lines from both faucets go to a T right before the solenoid.

I'm exited about this!
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Old 02-24-2019, 02:24 PM   #9
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+1 for the OP on calling out a real issue for boondockers.

I've thought about this issue myself, but rather than trying to retrofit an engineering control such as a manual or automatic valve, to date I've chosen to apply several administrative controls.

By that I mean, I have not yet aspired to return the first (and probably second) flush to the fresh tank. Instead, I make use of it in various ways:
  1. Top off the dog's water bowl - she drinks a lot of water when we are camping due to the exercise, exertion, etc.
  2. Set it aside in a pot to boil later for cooking (tea or cooking noodles, rice, etc.).
  3. Capture it and fill our fridge containers which make us cold drinking water
  4. Capture it in a silicone bucket for dolling back to the hot water that eventually comes out. Sometimes I crank the water heater and make REALLY hot water in it - maximum temp. Well, I can't use that straight up - it's too hot. So I used the diverted first flush water to bring down the temp of the water in the sink or bucket into a use-able range.

Just in case there's any reader scratching their head over why this would be a concern to anyone, here are my estimated numbers. There's no way that I'm going to waste somewhere between a quarter to almost a half a gallon of water during each heating event while boondocking. I only have a 26 gallon tank which I never fill with more than about 20 gallons (details omitted). It gets consumed quickly; it can't be wasted.

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