(Fresh) water leak at toilet.

j-d wrote:
They have a little plastic valve that opens when you push Flush. Rod going into valve is steel. There can be rust or wear where the rod goes in, and sometimes the plastic will crack. Can crack over the winter if valve wasn't winterized.

If you don't have a shutoff valve in the toilet supply line, add one while you're on this project. There are valves available at big box stores that just push onto the PEX tubing. Got ours at Lowe's. Our AquaMagic-IV has a vertical supply line. I was adding a pedestal base to get up to chair height and it worked out that I didn't have to shorten the cut PEX for the valve. Height of Pedestal matched Depth of Valve.

Toilet's more likely to have leakage problems than other fixtures in your RV, and it's the only one that'll leak onto the floor. Being able to shut it off lets you use the rest of the plumbing while you figure the problem out.

X2 on installing a shutoff valve. I just went through the same problem you are having this spring. Without having a shut off valve the project became a big time pain as I was in Mexico and a long way from the needed parts. I now have a shut off valve installed!

They have a little plastic valve that opens when you push Flush. Rod going into valve is steel. There can be rust or wear where the rod goes in, and sometimes the plastic will crack. Can crack over the winter if valve wasn't winterized.

If you don't have a shutoff valve in the toilet supply line, add one while you're on this project. There are valves available at big box stores that just push onto the PEX tubing. Got ours at Lowe's. Our AquaMagic-IV has a vertical supply line. I was adding a pedestal base to get up to chair height and it worked out that I didn't have to shorten the cut PEX for the valve. Height of Pedestal matched Depth of Valve.

Toilet's more likely to have leakage problems than other fixtures in your RV, and it's the only one that'll leak onto the floor. Being able to shut it off lets you use the rest of the plumbing while you figure the problem out.

Just a thought...does this issue happen when you are at some camp grounds and not at others?

If so, sometimes vacuum breakers will "weep" if the in-coming water pressure is high.
Do you use a water pressure regulator?

Maybe it's certain campgrounds with very high water pressure.

Moved from Forum Technical Support

Yes there is a vacuum break on water supply to toilet.......it is after water valve prior to entry into toilet.

Nothing more than a container with a hole in top which gets closed by a flapper when water enters. Then when water valve is closed.....water drains from container and flapper is opened.

Sometimes they don't close fast enough or fully close due to crud

You can go to thetford.com and look up your specific model where you can then open an exploded view of toilet and parts

Remove and rebuild the water fittings. A toilet is something you only want to repair once. SO a complete rebuild of replaceable parts is the cure. Valve vacuum breaker seals etc. Do it all unless you like shilly jobs