Tuesday, December 6, 2022


Fixing a leaky toilet valve seal


By Russ and Tiña De Maris

One of the more frustrating aspects of RVing can be dealing with odors in your bathroom. Chemical manufacturers have made tons of money selling a variety of brews and drop-ins, all said to eliminate the odors, and largely emptying pocketbooks. At times the real problem isn’t so much what’s in the black water tank, but a poor seal at the bottom of the toilet that allows that black tank odor to migrate back up into your bathroom.

An oft-cited culprit: the blade valve used in many RV toilets. The blade valve rests at the bottom of the toilet bowl. Its function is to hold water in the toilet bowl and to prevent gases from coming back up. Step on the toilet evacuation pedal, the blade swings back, allowing the contents to drop. Lift up off the pedal, the blade swings back, forming a water- and gas-tight seal. Or so it goes in theory.

In practice, however, things can happen to prevent the valve from making a tight seal. RVers have thrown up all sorts of “fixes” for this problem — they’re a staple of RV forum group discussions. Very often a “cure” that’s shared is to open the blade valve and then apply some sort of grease —often advised is petroleum jelly — to the rubber seal that the blade valve seats in.

Please don’t follow that advice.

Putting any sort of gunk that contains a petroleum product on that rubber seal will simply cause it to degrade — and more than likely create a situation where it will leak even worse. Here’s the advice of professional RV repair technicians:

First, get a handle on the issue. Often the cause of the leak between seal and blade valve is that “foreign material” (we don’t mean stuff made in China) gets caught in the rubber seal. That unwelcome gunk can create gaps where water and gas can pass. Get rid of the foreign material and often you’ll get rid of the leak factor. Take a round toilet bowl brush in hand and step on the evacuation pedal to open the valve. Now scrub all around the rubber seal to release the junk. You may need to repeat this a few times.

Did it work? Great! No? Well, more difficult measures may need to be brought to bear. This may call for actually disassembling the toilet to access the seal and giving it a more careful and thorough cleaning. Before reassembly, coat the seal with something that will not damage the rubber seal. One recommended product is Dow Corning 111 Molykote, which is a sealing compound specifically made for use with rubber seals — the stuff won’t damage them. It’s not real cheap, but can be found on Amazon.

Push come to shove, you might even have to replace the seal. Whatever you do, pass on the petroleum.

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