Thursday, September 28, 2023


Ask Dave: Our RV’s toilet won’t hold water – Help!

Answers to questions about RV Repair and Maintenance from RV expert Dave Solberg, author of the RV Handbook and the managing editor of the RV Repair Club. This column appears Monday through Saturday in the RV Travel and RV Daily Tips newsletters. (Sign up for an email reminder for each new issue if you do not already receive one.) Today Dave discusses a reader’s complaint that their RV’s toilet won’t hold water.

Dear Dave,
“2021 Puma destination camper. Toilet doesn’t hold water. Can’t soak to clean, or have water in it so when you do #2, it flushes easier. I cleaned around the seal after we got it and it started to hold water. Now it’s not again. I can hear the water going into the black tank. We got the Puma in June this year.” —Kathy

Dear Kathy,
The first thing I would recommend is to contact your dealer or the Puma Owner Relations Department to document the issue you are having as it should be under warranty. Even if you are going to attempt it yourself it needs to be documented in case you have other issues down the road.

There are a variety of toilet brands and models. However, the most common are Dometic and Thetford. Both use a similar method to seal the bowl and hold water. Economical units have a ball-type valve that rotates when the pedal is pushed. Other models have a spade valve that slides shut. Both utilize a rubber gasket commonly called a blade seal that the valve pushes against to create a seal that holds water.

Something could be preventing the valve from sealing

Since you indicated cleaning the seal did work for a short period of time, I would suspect something is getting in the groove of the seal and preventing the valve from making a full seal. This could be calcium or lime from extremely hard water, which can be filtered at the campground source. I have found some water has small sand particles in it that can clog up almost everything. I would suggest using an inline filter and cleaning the valve and seal more often. Also, Thetford makes a toilet seal cleaning product that I would use more often.

It could also be that your seal is getting dried out and becoming hard and brittle. This will also prevent it from sealing and holding water. The Thetford product can also help with this as it is lubricated. It conditions the rubber, making it softer and creating a better seal. If the problem starts to occur more frequently while trying these procedures, it’s time to replace the blade seal.

Read more from Dave here

Dave Solberg worked at Winnebago for 15 years developing the dealer training program, as marketing manager, and conducting shows. As the owner of Passport Media Creations, Dave has developed several RV dealer training programs, the RV Safety Training program for The Recreation Vehicle Safety and Education Foundation, and the accredited RV Driving Safety program being conducted at rallies and shows around the country. Dave is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.


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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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Thomas D
2 years ago

After a trip and before the next one I pour rv anti freeze into the toilet. It doesn’t evaporate quickly and keeps the seal moist. It helps, I believe. Also put some in the traps just like you are winterizing.
Helps keep the trap from drying out and stinking up the rv

2 years ago

It’s quick and easy to replace the rubber seal. Watch a couple YouTube videos. Cost is about $13.

2 years ago

Keeping the rubber seal clean & pliable is important, but there is another issue that can be causing the leak problem. Many new rvers release the foot pedal slowly when flushing. Dometic customer service will tell you that you need to slide your foot off the pedal & let the pedal snap back up. This makes sure the ball valve completely closes & seals off the opening. Over time, the friction between the ball valve & the rubber seal will prevent complete closure unless you allow the spring loaded foot pedal to “snap” the ball valve back into place. Some people don’t like the noise it makes, that announces to everyone in the rv that they are flushing, especially in the middle of the night. But it is necessary & the spring is designed to handle the snapping action.

Glen Cowgill
2 years ago

Dave, we had a similar situation in an old motorhome, I cleaned the seal and put a thin layer of Vaseline around the seal. It never leaked again for the 3 years we had that MH.

2 years ago
Reply to  Glen Cowgill

I agree. I use a special lube that is seal safe for rubber. The key is to clean the seal upper and lower side (with gloves of course!) Turn water pump off, then open valve, lube underside and top, along with a light coat on the ball valve. No leaks! Do this on a semi-Annual maintenance. Always keep water above ball valve level while in store mode. If the seal runs dry, it will crack and require replacement.

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