Tuesday, September 27, 2022


How to find hidden fresh water leaks

Dear Gary,
Unfortunately, my husband did not properly winterize our Southwind. 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 are not around any plumbing pipes. There are leaks by the storage bins and around some electrical wires. There are no leaks under the kitchen sink and no leaks under the shower or toilet or bathroom sinks. How do we fix the leaks if we can’t find where they are? 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. 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.

Read more from Gary Bunzer at the RVdoctor.com. See Gary’s videos about RV repair and maintenance.




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Bill Lively
3 years ago

My water leaks are coming from black and gray water tanks. The water is trickling over the side. This is fresh water. Any suggestions.

Jo Brillant
3 years ago

My fifth wheel has a leak in the floor .how do I get to it it’s in back of the fresh water tank.

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