Dear Dave,
I need help finding a water leak. While out, I woke up to a spot of water on the RV floor. I cleaned it up, and noticed no further water after that. The RV was connected to shore water, without pressure regulator. My mistake.
Several days later, another wet spot showed up on the passenger side of the RV, in the same general area. Cleaned it again.
When home, I removed paneling over the wet spot area. Could not see any trace of water.
I then applied 90 psi of air to the water lines, looking for either bubbles or water forced out of the lines. No joy.
Today, I turned on the water pump, knowing that it would run if water was flowing. Again, no joy.
The water lines do have water in them. But, no new wet spots. The only thing unusual that I can find is one of the fittings on the PEX line to the water pump does not have a crimped fitting, but uses a typical hose clamp. However, there is no trace of water or disturbed dust. The location is under the bed on the passenger side of the RV.
There have been no additional wet spots over the last several days.
Any other methods to find the leak? Help. We leave for the FRVA rally in MO on Sunday.
I read your column every time you write. —Tom, 2025 Hoosier Custom Cruiser
Dear Tom,
Since it is now Tuesday, June 23, I assume you may be at the FRVA rally.
Potential “gremlins” regarding water leaks
There are several “gremlins” when it comes to water leaks, as the spot of the visual leak (location of the water) is most often not the entry point or actual leak. Another gremlin is whether the water is from a fresh water source, air conditioner condensation, or outside rain.
In a residential setting, a plumber would test the water leak to identify if it was soft water, which would mean it came from inside plumbing, or hard water, which would mean it was a ground water intrusion. Since most campgrounds do not have a water softener, any water found in your rig is most likely hard water. You could fill the fresh water tank with soft water from home or use a light dye to find out if it is coming from a water line or other source.
I would start by replacing the worm clamp with a PEX crimp clamp installed with a ratchet tool. I have not had much luck with worm clamps on PEX line.
Since it is under the bed, that most likely would rule out roof air conditioner condensation.
You did not state the model of your RV. However, I did see a few floorplans that had twin beds in the back. Since you indicated the location was under the bed on the passenger side, I believe your model has twin beds. I am not sure what “paneling” you lifted. Was it the vinyl flooring?
Moisture meter may be useful
The probes of a moisture meter penetrate carpet and flooring and can help identify what might be a hidden flow of moisture from either a leaking line, or even a roof or sidewall joint. You could purchase an inexpensive moisture meter from Amazon here.
It is important to document all conditions when you see water, which you did with the description of the city water connection, no pressure regulator, and other items. However, you did not indicate if it had been raining prior to seeing the water on the floor.
Rain can enter even the smallest gap in sealant on the roof, roof to sidewall, around windows, and even underneath when driving in rain. It can also enter higher on the vehicle and make its way through the hollow tubing of the framework. In that instance, what entered on the roof could show up on the floor.
I have also found that water can pool in framework or an overhead shroud in the Class C. Then, when you move the rig, the side-to-side movement of traveling makes the water slosh around and comes out even a few days after a rain. That’s why we call them gremlins!
Start with the new PEX connection. If you get water again, check with a local plumber to get the water tested or dyed to identify if it is from the fresh water or an exterior leak.
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I had a gremlin leak similar to what Tom described. Out of the blue, water on the floor, no stream just a small pool of standing water. I felt every pipe, fitting, fixture and clamp and found nothing. Everything was dry. My leak wasn’t constant either.
After many hours of banging my head on the wall, I discovered the source was the condensation pan for my refrigerator. We had enough humidity for it to accumulate until it overflowed from driving…..
I once had a traveling leak like you’re describing. Camping World found it after I failed. But, I knew it was serious when the under-belly of my pull behind trailer started sagging. I drilled holes in that underbelly and it took a long time for it to empty. Of course, I turned off the water. Oh. The water trickle from time to time was by the door to the bathroom. Not overwhelming there.
Diagnosis: Water line under the sink was an elbow coming from underneath the floor. It had a lead BUT most of the water was spewing DOWN the entry hole. Thus, the full belly. But, a bit of it was traveling behind my sink cabinet and behind the fridge to ultimately go under the wall.