Originally Posted by Bcborn
The water flush valve is prone to crack if not winterized properly.
You will find this behind the toilet on foot pedal side.
Ditto.. My bad, last year got me on that one. It is crucial to run antifreeze all the way to that valve. With our winnie I need to remove the bottom slide out access below the kitchen sink and then access the short piece of hose to stick it in the antifreeze. THEN most importantly bypass the hot water tank and then run the individual lines with the pump turned on.
Last year I got lazy and just gravity drained the systems, big mistake as the toilet valve froze and split causing a slow leaker that was difficult to track down.
Instead of just replacing the valve I replaced the toilet and now keep the original as a spare.
If replacing just the valve then it is crucial to obtain new seals, bolts and nuts instead of reusing the factory ones.
Either way the toilet will need to be taken off the mount to fix the valve.
The valve is available cheap on Amazon but I would not recommend getting an after market cheap replacement. The original dometic branded one is more expensive and available through most RV dealers or online here: