Thetford Cassette C402 or C403 Gasket???

Michael J

Active Member
Aug 9, 2018
117
There's a recipe somewhere on here to use bleach and let it sit for 24 hours or something? Very mild bleach otherwise it would damage parts.. then just flush until that smell is gone.

I fill right from our hose spigot. Been drinking it that way for years, lol.

I still want to know what the heck that part is!?!?!?!?!?!?!?! @NLB did you find anything yet? I've reached out to Thetford twice and had no response... pity, last year they were really great to deal with. Maybe I should call....
Ok had to replace the motor and found that the hose that goes to the water nozzle to the toilet the rubber gasket there did the same thing that our cap did and bloat out I will provide a couple pictures as even when I cut the wires to the pump the rubber coating on it too is bloated just wondering what other damages there maybe....the new 10$ pump is a little smaller around so I made a foam sleeve to take up the space so it won't rattle around
 

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Sjm9911

Super Active Member
May 31, 2018
11,730
Nj
Might be the chemicals left in the tank? Or just plain old water for years, who knows. Drain it at the end of the year. And clean/flush out the holding tank at the end of the year. I only had the pup a few years but did that and chemicals only in the holding tank, and never had a problem. When I got it I had to blow out all the lines and really flush it feom the strands of hod knows what, almost looked like plastic flotting around in the tank.
 

rob.mwpropane

Active Member
Aug 11, 2021
282
Ok had to replace the motor and found that the hose that goes to the water nozzle to the toilet the rubber gasket there did the same thing that our cap did and bloat out I will provide a couple pictures as even when I cut the wires to the pump the rubber coating on it too is bloated just wondering what other damages there maybe....the new 10$ pump is a little smaller around so I made a foam sleeve to take up the space so it won't rattle around

That's crazy. It's like 40x as big as it was?
 
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popup-flyer

Active Member
May 11, 2021
321
Central Texas
Having read through this and seen some responses I want to say that the water pump/flush system is completely isolated from the toilet/waste system.

Is is not physically possible for that foam you found to have come from anywhere except the the flush water tank /fill plumbing or someone screwing with you.

I had the 402C and never saw anything like what rob pictured.
 

rob.mwpropane

Active Member
Aug 11, 2021
282
Having read through this and seen some responses I want to say that the water pump/flush system is completely isolated from the toilet/waste system.

Is is not physically possible for that foam you found to have come from anywhere except the the flush water tank /fill plumbing or someone screwing with you.

I had the 402C and never saw anything like what rob pictured.
I understand completely what you're saying and agree. I studied the crappy pdf for parts, I investigated all around... nada. The best anyone has come up with is the gasket on the fill cup. I had changed mine so that would sort of make sense.. I'm not 100% sold on that idea, but I haven't had any issues either.

I'm stumped
 
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NLB

Active Member
Silver Supporting Member
Oct 10, 2021
392
West Palm Beach, Florida
I understand completely what you're saying and agree. I studied the crappy pdf for parts, I investigated all around... nada. The best anyone has come up with is the gasket on the fill cup. I had changed mine so that would sort of make sense.. I'm not 100% sold on that idea, but I haven't had any issues either.

I'm stumped
Ditto!
 

Michael J

Active Member
Aug 9, 2018
117
I understand completely what you're saying and agree. I studied the crappy pdf for parts, I investigated all around... nada. The best anyone has come up with is the gasket on the fill cup. I had changed mine so that would sort of make sense.. I'm not 100% sold on that idea, but I haven't had any issues either.

I'm stumped
I worked in the quick oil change business for about 7 years out of highschool you should see what happens to a brake cap rubber if the fluid gets contaminated it will about double in size it's crazy here is just a quick look on the net for a picture
 

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rob.mwpropane

Active Member
Aug 11, 2021
282
Mystery SOLVED... not really by me, but at least confirmed. I think @Michael J was the one who originally made the remark it came from the fill cap. For S&G I put the gasket inside the door and forgot about it, well low and behold here is that massive gasket! Shrunk back down. I added some original pics to compare...
 

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rob.mwpropane

Active Member
Aug 11, 2021
282
Mine shrunk too. And then I threw it in the trash. Might look for an o ring that fits, or might not. 🤷‍♂️

I had changed my cap (can't remember why, I think Thetford was nice enough to send me one?) so mine still had that o ring in there.. the ring had just been in the holding tank for who knows how long, lol. I don't see where it's really needed unless your tank is full and your on a steep embankment.. I could see a little water start to seep out... maybe... who knows.
 

NLB

Active Member
Silver Supporting Member
Oct 10, 2021
392
West Palm Beach, Florida
I had changed my cap (can't remember why, I think Thetford was nice enough to send me one?) so mine still had that o ring in there.. the ring had just been in the holding tank for who knows how long, lol. I don't see where it's really needed unless your tank is full and your on a steep embankment.. I could see a little water start to seep out... maybe... who knows.
I want you to keep your unit level, mister! And stay the hell away from all embankments and ledges.
 

Michael J

Active Member
Aug 9, 2018
117
What I would watch out for is where the water get pumped into the toilet the piece the hose pushes onto them it snaps into the ring from the inside and there is a o-ring there and that bloated the same as the cap and caused it to be loose and with vibration it all fell into the fresh water tank. Head off any problem and check it out may save from a headache later and is easy to fix with a small o ring
 

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