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Wednesday, December 17, 2014

RV plumbing "mod" saves wasted not-so-hot water

For boondockers, staying out in the "wilds" and away from civilization for as long as possible is often a priority. When we boondocked for entire winters on the desert, water was a primary concern – how do you stretch 40 gallons of fresh water between two people for as long as possible?

The usual water conservation techniques always apply: Take the "Navy shower," as an example. Step in the shower, wet yourself down, turn off the water. Soap up. Turn on water, rinse off. It's practically a contest to see who can use the least amount of water and still come out clean. Other water conservation techniques come into play – save the dish water for flushing the toilet. We've even heard of extreme measures – one RVer uses a bucket and takes gray water out of his holding tank to flush the pot. Not so sure on that one – our gray water never smelled good enough to bring back inside the rig.

But what about wasted water when waiting for hot water to make its seemingly sluggish way from the water heater all the way out to the faucet when you're waiting to wash your hands, dishes, etc? Some (ourselves included) have used a jug or pan to collect that otherwise clean, fresh water, and use it later for "cold water" purposes. But it can be a bit of a hassle, and if you're using a tankless "instant hot" heater, or if your conventional water heater is a long way from the faucet, you can collect quite a bit of tepid water while waiting. Here's an RV modification to think about.

Rather than collecting that tepid water in a pan, instead, simply re-route it with a modified plumbing scheme to send it back to the fresh water tank. How so? By putting a "T" in the water line that supplies the "hot" side of your faucet. One of the T outputs routes to the faucet, and the other side to an add-on line that routes back to the fresh water tank inlet. The trick is to put a valve in the line headed back to the fresh tank. When you want hot water at the faucet, leave the faucet turned off, but open the re-route valve long enough to ensure you really have hot water on location. Now close the valve, and use the faucet – and have hot water readily available.

You could really trick this idea out by using a 12-volt electrically operated solenoid valve in place of a standard water valve. Push a button at the sink, the solenoid opens, shunting tepid water back to the fresh tank; when the hot has arrived, let loose of the "normally open momentary contact push" style button. Here's one solenoid you could use, for less than $25.00.

Of course, you'll need access to 12 volts, and a way to route the "new" line back to the fresh water tank on your rig. It'd really only make sense if your tank is on the same side of the rig as the faucet(s) you want to modify, but hey, it's a great afternoon "mod" project for the boondocker.


  1. That is a great idea....we have such a device in our home called "The Lobster" It is hooked up to power and one side to the hot water and the other to the cold side of the sink in our bathroom. The bathroom is 50 ft away from the hot water heater. You push a button and the little pump moves hot water back into the cold water side until it reaches a pre-determined temperature and then shuts off. Then when you turn on the faucet you have hot water and continues as the hot water pipe has been "primed" for lack of a better word. Save us many gallons of water....we have been using this device for years before our California drought. Just made sense to not waste water waiting for it to get hot.

  2. Yes the first comment is great because there is NO need to run a separate water line back to the supply tank. We use a small pump like the cheapest RV 12 volt or even a circulator pump like run from hot line to cold line under the sink. You can use a timer or thermostat, but simpler just a pushbutton, count to 20, and release does the job.