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Cassette toilet seal replacement

jebjamjebjam Member Posts: 50
in Heating/Plumbing & Winterizing
I'm surprised to find no discussion thread about owners replacing the rubber seal on the cassette toilet. We noticed an odor in the bathroom of our 5 year old 320 CS-S and found liquid waste from the toilet on the outside of the cassette and in the compartment, basically untreated pee collecting in the cassette compartment. Thetford's owner's manual advises the rubber seal is subject to wear and should be replaced time to time (think I read every 4 - 6 years?). YouTube videos show how to replace this and that a worn seal is responsible for the leak.
I've seen posts about keeping the seal clean and lubricated and the post about the silly cover over the small compartment under the cassette that can cause a poor seal if it dislodges and lifts the cassette, but nothing about seal replacement. Given Thetford says this is a maintenance issue and the leak we're experiencing is pretty significant and nasty, I'm surprised others aren't talking about having this issue and whether replacing the seal works. 
I've ordered a replacement seal and will be doing that soon, hopefully it's the fix. It wasn't easy to find the part (the owner's manual doesn't list the part #), 23721 is what I ordered hopefully that's correct.
Wondering if others have experienced this?
2021 T@B 320 CS-S Boondock / 2020 Ram 3.0 EcoDiesel
Golden, CO
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Comments

  • Basil48192Basil48192 Member Posts: 401
    @jebjam
    This is the first I've heard of this....though I did have trouble keeping a good seal until I removed the plate you mentioned.  It prevented the cassette from latching in place and creating a tight seal.
    I will order a seal just to have on hand.  Thanks for the heads up!
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  • jebjamjebjam Member Posts: 50
    Can you tell me how you knew it was the plate causing the issue? I have looked at that and it seems to be in place but I suppose it's possible it's still the problem. The issue I'm having is the seal not working, I assumed since Thetford says it wears that's it, but I don't know that and haven't yet replaced it to prove it's the problem. The plate in mine seems flush and stays put, I assumed that meant it's ok. 
    Given nobody is talking about this, even though Thetford says it wears out, I'm suspicious I may be wrong. We use our camper moderately, certainly not as much as many on here.
    The issue we have seems to be the bowl not holding whatever's in it in the brief time before we flush, and said "stuff" finding its way into the compartment outside the cassette. Its nasty as it sounds.
    2021 T@B 320 CS-S Boondock / 2020 Ram 3.0 EcoDiesel
    Golden, CO
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  • Basil48192Basil48192 Member Posts: 401
    @jebjam.
    It makes sense that the seal could dry out and shrink over time.  I have used the Thetford Seal Conditioner periodically which may or may not have helped.  The seal on my cassette does seem to still be soft and pliable.  
    My original issue was definitely caused by that plastic cover.  With the cover in place, the little green latch would not drop into place, so the cassette failed to latch securely (see red arrow in the photo). 
    There is a small ramp at the rear of the compartment which drives the cassette upward when it is latched properly, compressing the seal against the bottom of the toilet opening.  If the green latch does not drop into place, the entire cassette can move forward, causing it to drop slightly and break the seal.


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  • Basil48192Basil48192 Member Posts: 401
    @jebjam.
    Sorry, I just re-read your last post.  
    It sounds like you are filling the bowl with water before using, then flushing it like a residential toilet.  
    I may be wrong, but we always open the toilet valve before using it.  We never leave 'standing water' in the bowl.  After use, we flush it thoroughly, periodically opening and closing the 'flusher' to clean everything.  That being said, we only use ours for '#1'.  
    Either way, the latch issue described above still applies.  
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  • jebjamjebjam Member Posts: 50
    Thanks for the detailed answer and your photo! I too have used seal conditioner, but did not use it regularly the first few years. The seal looks fine but I know that doesn't always tell the story. Ironically I noticed the latch not locking in the past and didn't realize that would affect the seal, you give a good explanation of that thank you. I'm careful to make sure it locks now, and yet this year is when the problem started.
    I'll throw away the cover as described in your previous posts ( :)) and replace the seal, and hope one of those does the trick!
    2021 T@B 320 CS-S Boondock / 2020 Ram 3.0 EcoDiesel
    Golden, CO
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  • jebjamjebjam Member Posts: 50
    Basil48192 said:
    @jebjam.
    Sorry, I just re-read your last post.  
    It sounds like you are filling the bowl with water before using, then flushing it like a residential toilet.  
    I may be wrong, but we always open the toilet valve before using it.  We never leave 'standing water' in the bowl.  After use, we flush it thoroughly, periodically opening and closing the 'flusher' to clean everything.  That being said, we only use ours for '#1'.  
    Either way, the latch issue described above still applies.  
    To clarify we don't fill the bowl before use, but we also don't open the latch before using it. We also only use it for #1, unless there's a boon docking emergency. Our practice is to void with the latch closed, open the latch to flush then do the same as you, using short pulses of flush opening and closing the valve. We never leave standing water in the bowl, but urine is briefly in the bowl before opening the valve after voiding.
    After 4 days of camping, opening the valve before use would cause some odor from the cassette to enter the bathroom, don't you have that happen? We use Happy Camper treatment and like it, but 4 days of standing waste in 90 degree weather it still has some odor.
    I think opening the valve before use would help prevent the problem, eliminating the brief standing urine in the bowl, but seems you shouldn't have to do that and it'd be unpleasant?
    2021 T@B 320 CS-S Boondock / 2020 Ram 3.0 EcoDiesel
    Golden, CO
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  • Basil48192Basil48192 Member Posts: 401
    I haven't really noticed an order issue by leaving the hatch open briefly, but it sounds like we are basically doing the same thing, leaving liquid in the bowl for as short a time as possible.  

    One last thought as I was looking closely at mine.  I wonder if a little shim of some sort between the green latch and the white plastic would force the cassette further back and upwards.  I wouldn't bother unless you continue to have issues, but thought if might help.

    Good luck!!
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  • jkjennjkjenn Member Posts: 6,412
    Before replacing it, I recommend trying to restore it with the Thetford product meant to treat and restore RV toilet seals: https://youtube.com/shorts/Mpm8AltiAoc

    2021 T@b 320 Boondock "Mattie Ross" | 2021 T@b Nights: 239 | Total nights in a T@b 455 | 2022 Jeep Grand Cherokee L Overland | T@b owner since 2014

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  • jebjamjebjam Member Posts: 50
    jkjenn said:
    Before replacing it, I recommend trying to restore it with the Thetford product meant to treat and restore RV toilet seals: https://youtube.com/shorts/Mpm8AltiAoc
    Thanks for the suggestion, good idea, but I tried this a couple of times with that exact product. I'm wondering if Basil's cover issue isn't also mine, just because no one else seems to have had to replace their seal this early into ownership.
    I am certainly going to use the restore solution regularly from here on regardless. 
    2021 T@B 320 CS-S Boondock / 2020 Ram 3.0 EcoDiesel
    Golden, CO
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