mine started leaking a few years back after a prolonged sit in storage. The water in the bowl had dried. I tried almost everything I read in forums or could think of. tried throwing money at thetford buying their seal lube products, etc... all no luck
finally ordered a new seal...but before I did the job, I tried soaking it for a few days with clr...poured some in the bowl, let it soak a while....overnight...worked the valve open and closed, let it snap shut a few times, etc.... repeat. After a few days of this it seemed to be sealing again.
As I mentioned, it was a few years ago and it's still working.
Now I'm careful to keep an eye on that bowl and keep it flooded. When putting into storage I pour a small bit of the blue tank treatment stuff right into the bowel along with some water. Seems like it helps slow the evaporation maybe... Oil I'm sure would work but I don't love the idea of oil residue in the bowl..going rancid..etc...
but now that I'm thinking about it writing this maybe some clear mineral oil would slow the evaporation and also lubricate the bowl and tank regularly without going rancid and without attracting bugs and such like some organics such as vegetable oil might... and the regular bit of oil in the tank might help minimize stuff getting stuck in there on the probes and such....
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