Don’t freeze the pipes of your RV

By Greg Illes

When we first bought our motorhome, we never figured we’d be out in freezing weather. Freezing means snow and ice and things that just aren’t fun to camp in (we thought). And when we weren’t using our RV (“Howie”), we parked him in our Mediterranean-climate driveway in central California. So we never gave much thought to frozen plumbing problems. We’ve never winterized the rig.

But even in our first year of ownership, we found that cold-weather travel was a secret delight. Beautiful scenery, no crowds, clear crisp frosty mornings. And temperatures near or below freezing. Uh-oh.

Add to that basic problem that we eschew RV parks and crowded campgrounds — our ideal camp is a boondock location with nobody else around, just us and the wide open spaces. Which means no power, no water, no sewer, and no fix-it folks to repair ice-cracked pipes. If we wanted to have the experience, we needed to be able to deal with nighttime temperatures in the 20s or even teens.

Fortunately, our Winnebago/Itasca was designed with enclosed plumbing — there are no pipes or drains exposed to outside air. In addition, the design has a small air bleed from the forced-air heater duct into the holding tanks area. However, this built-in “warmer” had a major drawback — it only worked when the forced-air heater was operating. You know, that noisy, propane-sucking, battery-draining forced-air heater.

With deep concerns about saving our plumbing from solidifying, the first thing I did was install a remote-sensor temperature thermometer in the outside water bay (I used this one, but there are hundreds available). With the display mounted in our bedroom, I could thus check throughout the night on the downward progress of the coldest spot that our pipes were exposed to. When it started to read in the mid-30s, I’d start up the cabin heater and we’d have to live with the noise and propane consumption.

On a few chilly occasions (14 F one night), we gave in and retreated to an RV park, where we could plug in a small electric heater and keep it on “low” inside the water bay. But that was just a workaround. We really wanted to be able to deal with the problem while boondocking, and that much heat would drain our batteries too quickly.

Around that same time, we learned the wisdom of using a radiant heater instead of the built-in forced-air unit, and it worked fine for keeping us warm, at 1/4 of the propane consumption and no battery drain or noise. But too bad, it did nothing to warm the water bay because the air was not being circulated. I knew that I needed to get some heat into that water bay, somehow.

FINALLY, I DID SOME RESEARCH on where all the Itasca water pipes were routed. (This was really easy with the outstanding documentations supplied on-line by Winnebago.) Based on this new knowledge, I identified a spot in my bathroom inside wall where I could mount a small fan. The fan would blow warm cabin air down inside the wall cavity, and out into all the areas where piping runs. I made sure that there were places at the far ends of the cavities, where the air could flow back into the inside of the cabin, so it’s a true recirculation design. (One return spot is under the kitchen sink, one under the bath sink, and one under the bed.)

I tested the airflow using a special meter, but it could be done with a candle flame or small bit of smoke-generating tinder. All that’s necessary is a very modest flow to keep the air moving even a little bit.

Now we use the efficient, quiet catalytic heater to keep the cabin in the 45-55 range (we like to sleep cool). The recirculation fan distributes the air through the hidden spaces, and my remote thermometer assures me that the coldest spot never drops below 35-40 F. The real beauty of this solution is that it consumes so few resources. The fan draws only 0.16A, for virtually invisible battery consumption. And we only have to turn on the radiant heater, and only when the cabin drops to 50 F or less.

HOW TO DO IT
If you want to tackle this, you’ll need to be the kind of person they call “handy.” You will need to understand the physical routing of all your plumbing, either from documentation or by inspection. You’ll also need to be comfortable tapping into your vehicle’s 12V wiring.

If you have exposed pipes, the situation is not hopeless. But you will have to shroud them, box them, and/or otherwise insulate them from outside air exposure. Note that most of the common solutions to this issue involve heated pipe wraps or sheets (well beyond the capability of battery support); if you are okay with being tied to power hook-ups, that’s fine. We weren’t, and we opted for a super-low-power solution.

Here are the design issues I considered. You may have others as well:
• Recirculation — the design must flow cabin air across all at-risk piping, and back into the cabin. Without this path, the air won’t flow. If the exit is to the outside, you’ll be cooling your cabin down when you least want it.

• Low noise — Depending on where it’s mounted, the fan has to be quiet. Even the low-noise ones sound about like a desktop computer. Aim for a spec of 25db or less.

• RPM — Slower fans are quieter but produce less air. This requires a careful trade-off.

• Bearings — NEVER buy a sleeve-bearing fan; they just don’t last. Get ball-bearing or hydraulic.

• Low power draw — The fan should run off 12V and draw very little from your batteries. Anything below 0.25A should be fine.

• Adequate air — The fan needs to push enough air around to keep the serviced areas above 35 F. The really wimpy fans won’t cut it — look for 40CFM or more.

• Diameter — small fans are noisier and have less airflow than larger fans. Try to stick with 5-inch or larger.

• Color — My mounting location was in the middle of a pale-white wall, and a big black electronics fan (the usually available configuration) would have been pretty ugly.

• Screens — I didn’t want to use a close-weave screen, even though it’s better looking. They reduce airflow too much, so I used a metal grill type.

• Mounting clearance — Fans need about 1/2 their diameter in clearance to achieve their target airflow. You can’t mount one an inch away from a flat surface, because the blades will stall and not produce any flow.

• Control — I used a simple panel toggle switch to turn the fan on and off. I thought about a timer switch, but I’m up several times a night anyway (aging prostate), so it’s no big deal to manage the fan. It’s right above the toilet anyway.

The fan I used was a thin white unit I got off of Amazon, but it’s apparently no longer available. Here’s a link to a similar fan. With a low power draw, I simply found the nearest 12V circuit and tapped into it.

Our nights are quiet again, and the peace of mind helps with my “inner silence” as well. Total cost was about $20 and several hours of figuring and fiddling.

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