Thursday, March 23, 2023


RVers can’t find water leaks to fix them. What’s wrong?

RV Doctor

Dear Gary,
Apparently my husband did not properly winterize our Southwind motorhome. When we fill the fresh water tank we have no problems, but when the pump goes on the leaks start. When we roll under the RV the leaks aren’t around any plumbing pipes. There are no leaks under the kitchen sink, and no leaks under the shower or toilet or bathroom sinks. But there are leaks by the storage bins and around some electrical wires.

How do we fix the leaks if we can’t find where they’re coming from? Where should we look for leaks and how do we get there? —Jacque

Dear Jacque,
If the fresh water system was not drained completely or properly, the water heater could have ruptured or, at the very least, a fitting could have been damaged. Check for water around the water heater tank first; be sure to feel around it as much as possible because the tank is surrounded by a foam shell. If the tank is damaged the water may be somewhat contained by the foam. At the rear of the water heater, from inside the coach, check the outlet fitting at the top and the cold water inlet at the bottom. If you have a water heater bypass valve kit installed, check those valves for dripping also; likewise, for any water filter or purifier in the system.

It is also possible that the pump itself has ruptured; inspect the pump head for leaks. Water will always seek its own level and flow down but it won’t necessarily be in the most direct way, so the areas where the water is dripping from the coach may not be where it’s actually leaking from. Check all lines and fittings in accessible areas. Don’t forget external areas like the outside showerhead, if so equipped. Trace the plumbing as far as you can from the sinks, toilet, pump and hot water tank. If you cannot locate a leak in the areas mentioned, then it could be that the leak is under the floor or behind a wall. In this case you should probably seek professional help.

Access for plumbing repairs is normally accomplished by coming up through the bottom whenever possible rather than down through the floor. Another option is to fully drain the water system and use pressurized air (50 – 60 psi) instead of water pump pressure. A fitting called a blowout plug can be attached to the city water inlet and compressed air injected. This will eliminate the water mess as you search for each leak. A soapy solution can be applied to fittings just like leak testing an LP system. Bubbles will form at the leak.

Freeze-damaged tubing will be quite evident. You’ll see bulged portions with a slit running in the same direction as the tubing. The good news is ruptured tubing can be easily cut out and replaced using new fittings. The bad news is that there may be several ruptures. You’ll have to run a pressure test (air or water) after each repair is completed until the system will hold pressure for about ten minutes. Wish I had better news for you, but the remedy is easy once you locate each leak in the system.

[Comments are now closed on this article.]

gary-736Gary Bunzer, the RV Doctor, died April 17, 2020, from COVID-19. Gary contributed to almost from its beginnings 19 years ago. Gary posted this article in January 2019. We know that Gary would be happy that we are sharing this advice with RVers again. For more than four decades that was his mission.



0 0 votes
Article Rating
Inline Feedbacks
View all comments
4 years ago

If I may, put food coloring, you’ll find the leak faster

4 years ago

The first thing I would check is the strainer at the water pump. Next check low lying plumbing fittings, they break first before plastic tubing. If the water wasn’t siphoned out it the water heater it may have split.

Sue Spencer
4 years ago

We also developed a leak that sounds very similar. Every time we turned our water pump on or hooked up to pressurized water it leaked. We could see it was coming from under the floor somewhere, but not able to pinpoint the location. We ended up taking it in to be professionally fixed. Turned out to be hoses were worn through due to the slides rubbing on them. They tied them up so it shouldn’t happen again.

Richard D Stull
4 years ago

If your coach was plumbed with CVPC, I would start replacing all if the plumbing with PEX. Have repaired several over the years.

Lisa Cantrell
4 years ago

We thought we’d developed a leak from our fresh water tank because of the location of the leak However, it was the water line to the ice maker. Right at the top as it goes into the wall the pipe was broken. With the ice maker on it would request water. It seems a small amount was getting through so it was making ice but also flowing out as the ice maker tried to refill.

4 years ago

This is why You need a BYPASS on your water heater and RV Plumbing. You need to completely drain the RV Water Heater. Since it would be extremely expensive to fill the Water Heater with Anti Freeze. If you are in a COLD Weather State, it is critical that Winterizing your plumbing is a REQUIREMENT!

I live in Louisiana and still Winterize my RV. Even though we don’t get too many super freezing days down here, it still happens.

And I do it myself, since I don’t trust most RV Dealers to do the job right!

Draining your Water Heater also gives you an opportunity to check the Probe if you have one in the tank and replace it, if needed in the spring time.

Dave Telenko
4 years ago
Reply to  Jeff

Hey Gary that was well thought out explanation on how to find that fresh water leak. It can very devious in finding fresh water leaks in an RV!

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.