How to save every drop of “get warm” water


By Greg Illes
Here’s a story for the “fiddlers” among us. If you’re not super-handy, and not much into fiddling with your RV, this will likely be of only academic interest at best. But if you love tweaking your rig and getting the ultimate best out of it – well, read on.

For years, Karin and I would save our “warmup” water – you know, the cold water that comes out the hot faucet until the hot water from the water heater finally gets there. We’d run it into a jug, and then use that water for toilet flushing, washing or other chores.

It wasn’t just a matter of being picayune (a wonderful word to replace the overused “anal”). In our Itasca Sunova, almost 1/3 of a gallon of tepid water would flow before the temperature got usefully hot. Since we are frugal with water, our 75 gallons lasts us for 10-12 days, and even at only one warmup per day, that would still be 0.33 x 10 = 3.3 gallons, more than a half-day’s usage wasted. And if we take our showers at different times (often true), double that number. Plus, when you’re water-conscious, it is just plain painful to watch good water go straight down the drain.

Well, after a while we discovered that we didn’t really need all that 2/3 gallon of water every day for miscellaneous tasks (especially after we converted to a composting toilet with no flushing). And one time, we accidentally spilled half the jug onto the coach floor. Yuck. So I began to think about how to hold onto that warmup water, without the middleman (jug).

Since we almost never use hot water from either the kitchen or bathroom faucets, the primary culprit was the shower. What I needed was a way to “recirculate” the water from the shower, back into the fresh water tank.

I puzzled over this for literally a year or two, coming up with Rube Goldberg ideas of hot water recirculation pumps and such. All of the ideas were complicated, and none got the hot water all the way out to the actual shower head; recirc pumps only get it to the valve, which would still result in a jet of cold water at the start of a shower – either on my body (egad!), or down the drain (rats!).

Finally, after endless poking around the bowels of my coach’s plumbing, I found a reasonable, cheap, and low-complexity answer. It’s so simple, I don’t know why it didn’t occur to me earlier.

  • I installed a fitting into an unused port on my fresh water tank. [NOTE: If this port had not been there, I would have used the vent line instead. That would have resulted in venting the tank into the shower – no problem.]
  • Then, I ran regular 1/2″ pex tubing down under the floor and up into the back side of the shower stall.
  • I crafted a “dump spout” out of 1″ PVC 45-fitting and tubing, and punched a hole in the shower wall to fit it. Tightened, glued, and sealed in place.
  • Finally, I made an adapter off the back of the 1″ 45, and hooked up to the pex line to the fresh tank.

That configuration gave me a direct line from the shower to the fresh tank.


Voila! Now all we have to do is push the shower head up against the dump spout, turn on the hot water and count slowly to ten. All the tepid water gets pushed right back where it came from – into the fresh tank.

The installation looks really clean and “professional.” It takes no power, no wiring, and no moving parts. I even added a stainless steel screen, just to prevent any sizeable object (or critter) from entering the plumbing. I’m really happy with how it looks and how it works, and we never again have to mess with a jug.


  • If your lifestyle also uses hot water from the kitchen or bathroom, you may find a way to use this concept, but from a different location than the shower. Everybody’s needs are different, and of course YMMV.
  • You need to be a little nuts to tackle a job like this for the sake of a few gallons of water – but let’s face it, a lot of us (including me) qualify.
  • If you do decide to mess around with a project like this, be advised it’s not for the faint of heart. You need to thoroughly understand your plumbing system, including venting, before you start.
  • You have to be familiar and comfortable with RV plumbing fittings and procedures.
  • If you design it wrong or do it wrong, you could flood your RV or ruin your fresh water tank, or some number of other things I haven’t thought about.
  • In other words, be careful, think it through, test it thoroughly.

And of course, have fun doing it. I sure did.

Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. 

##RVT819 ##RVDT1379

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Brad Teubner
2 years ago

Not for everyone, but we run our warm-up water into the dog bucket.

2 years ago

This article reminds me of our campfire chats where we exchange Rv ideas to better our rigs. Ideas are offered, some good, some not applicable to our particular rig, but, they start me thinking, what if. Keep these how to articles coming! Good ideas.

Crystal Diane nappi
2 years ago

Brilliant. Love this. I often dry camp…and my small camper tank I save every drop. I don’t use my tap water for cooking or drinking. I carry water separately for these purposes.

bill bateman
2 years ago

Speaking of warm water … we had for a brief time a 1978 Execurive that used a hot water hose tapped from the engine heater hose to wrap around the hot water heater tank … thus heating the water in the tank through convection. Looked like a factory install and worked great! … Hot water available as soon as you parked. Has anyone seen this setup available aftermarket?

2 years ago
Reply to  bill bateman

I had a hot water heater in my Xplorer that had an engine water heat exchanger ( coil ) in the HWH er . It worked great but was seldom needed. Given its age ( 17 ) , the cost of replacing such a unit , and the condition of the approx 50 feet of old heater hose running to and from the heater I abandoned this feature while changing all the other vehicle hoses.

2 years ago

Here is a well designed system that accomplishes the same thing. I haven’t installed one, but if we still dry camped as much as we used to I would.

Charles Davis
2 years ago

Saw a system with same results don with a return valve on the hot side of the sink back down to the tank, ie it was a closed system, just turned the valve one way and the hot water ran into the bath sink and the other way it was returned to the fresh water tank, count 18 seconds and turn the valve back to the sink and you have saved the “warmish” water. I saw this in a 1978 Newell that was owned by the most innovative full timers I had ever met. He had used the bath sink as his valve placement as it was after the hot water “T” for the shower, at the furthest point from his water heater and only a few feet past the shower “T”. A fully closed system so no shower water contamination!

2 years ago

Too many people with short horizons.

Wolfe Rose
2 years ago

I agree with the cap requirement – soap/body backspatter would get in, and girls with long hair splash shampoo everywhere it seems.

Otherwise, awesome writeup!

2 years ago

Looks great, although I’d put some kind of cap on it to seal it up when not in use.

Tommy Molnar
2 years ago

I like this idea, but with our fully enclosed tanks I’m not sure how I could access the fresh water tank. I guess I’m one of the “faint of heart”. Ha.

Richard Heberlein
2 years ago

Too much potential for contamination.