toilet

Clean the seal and lube it with plumbers silicone grease. (nothing petroleum based!) If that doesn't work a new seal is usually not hard to install depending on what toilet you have.

I have found that the grove that seats the piece that opens and closes will get filled with TP. I have taken a cloths hanger wire and cleaned out the grove. Along with lubing the seal check out the grove.

Good Luck

There are two styles of toilet. One has a "Ball" shaped Dump valve and the other a Gate valve.
The Ball Valve types come with a tool to clean the seal.. I've never actually used it but did clean by other means..

The other (Flat gate valve) ( I do not recall a tool. but again cleaning may help.

As mentioned, we need to know the style of valve.

One other thing not mentioned is to look for mineral deposits on the valve. Both styles rely on a smooth plastic against the rubber seal. If you get mineral built up, that can cause it not to seal.

If it has the black rubber gasket at the opening just replace it! It takes less than 5 mins. you can get it on Amazon cheap!

The seal is easy to replace but try plumbers' grease first.

Hello
I have the ball type can I change the seal from the top ? Thanks Kenny

I have the Thetford Style II,with the ball type gate. It's been leaking through for the last couple of years, so I finally changed the seal after watching a couple of YouTube videos on how to do it. Very simple. One guy coated it with plumber's grease, so I did that too. It was good for about 2 weeks, then started to leak through again. WTF!! It seems that the real reason is that the ball isn't quite rotating fully closed,so yesterday I sprayed silicone on everything I could see where it pivots and moves and it seems to come to a more solid stop upon release of the pedal now. We'll see how long it lasts. This wastes too much water when dry camping. I'm getting ready to switch to a Dometic!
JK

You should definitely check the grove! Lol

Well, the silicone spray only lasted a day, so today I decided to take it apart again and realized that the rear facing end of the ball (the ball closes front to back) has a larger gap than the front end and relocated the seal slightly to give it a little better coverage on that end to seal more completely instead of the chance of a small gap. See if that works.