Help, we’re boondocking in the Desert. I have a Thetford Style II that is filling up quickly on its own when the water pump is on! Could this be the flushing mechanism in the back of the toilet or something else?

Is it filling to overflowing, or just a half gallon or less? If it continues to fill/overflow, I would suspect the mechanism is sticking or broken.Easy thing to try, operate flush handle/pedal and let it snap closed. Worst case, you may need to plug supply line to toilet, and use other water source for a manual flush.Is there a handy guy camping near you, that may be willing to check the valve serving the toilet?Jerry

The valve on my toilet did something similar. I temporarily fixed it by installing a sharkbite shutoff in the line behind the toilet. Then you can fill the toilet as needed by opening and closing the valve without disrupting the water supply elsewhere.

It could be a worn or damaged valve, OR it could be some schmutz got stuck in the valve causing it to not fully close. Try rapid opening and closing to see if the seal reseals. Try turning off the pressure and drain down the line a bit to see if that dislodges any gunk. You can even shut off the water, disconnect the line and blow some low pressure air into the toilet while working the valve to see if that helps.A couple years back I had a sticking valve. I shut off the water, removed the line and squirted some liquid dishwashing soap into the inlet while opening and closing the valve. After reconnecting, no more stuck open valve (I did replace it anyways later that year as a precaution).if those don't do it, you'll need to make a temp fix like MFL or gwalter suggested.

Thank you all for your quick responses and good suggestions! We did try snapping the flush pedal a couple of times. We will look to install a shut off or plug the water line tomorrow as a temporary fix.

Lakejumper wrote:Could this be the flushing mechanism in the back of the toilet or something else?There are two suspects and yes that is #1#2 is the linkages that operate the valve sticking and that's easy to eliminate by manually checking the valve to insure it's in the "Closed" position. NOTE. very easy to replace the valve.

Toilet Fills with Water Pump On | Good Sam Community

gtnsmlr
Explorer
Feb 08, 2022
Over the years of full timing, I've replaced all the parts on mine a number of times. the water valve, if needed is a simple fix. I've noticed that the valve Is prone to leakage if the water pressure is low, give that a check. If you have access to the pedal side you can replace the valve parts without removing the toilet but for the first time pull the toilet, getting the peddle back on is a chore and best done o n the table with a beer. I actually like the style ll, you can rebuild all the moving parts in 15 minutes once you get it out.
Veebyes
Explorer II
Feb 09, 2022
On my 'to do' list this spring during the annual boatyard refit. Mine developed an annoying intermittent leak last year. Took the foot valve apart & put it back together a few times as we were mid trip & not anywhere to get a new one.

Cheap & easy part.

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