How to DIY Replace a Thetford RV Toilet Waste Ball Seal

Having problems with the seal on your RV toilet? Replacing the waste ball seal in a Thetford RV toilet is a simple and inexpensive DIY RV toilet repair.

In this story, I walk you through the process, step-by-step to save you time, money, and avoid those unpleasant odors in your RV!

– Thetford 34120 Waste Ball Seal – Socket wrench or adjustable wrench – Disposable gloves – Plumbers’ grease or silicone lubricant

Parts and tools you will need:

Shut off the water to the RV system. Release the water pressure by holding the foot pedal down until the water flow stops completely. This will drain the water out of the toilet inlet water line and the bowl.


Using a socket wrench, extract the two long hex-head screws that hold the toilet bowl onto the pedestal. Keep track of the stainless steel and nylon washers, as well as the order in which they are used…metal washer at the top, nylon washer at the bottom


The toilet bowl removes easily with a slight counter-clockwise twist and lifting it off the pedestal. It can be carefully laid on its side on the floor by the pedestal.


The round waste ball seal easily lifts out and you can now thoroughly clean the seal recess area. You may have to do a little scraping to get the mineral scaling completely removed. Be careful not to damage the surface of the recess.


Coat the new seal lightly with silicone lubricant or plumber’s grease, and place it in the cleaned seal recess.


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