"Fluid" escape from Thetford Toilet Cassette

Hi there. So, here is the second problem today with my 1999 Symbol. Upon emptying the toilet cassette there was 'fluid' sitting on the top of the cassette and then after withdrawing this I see that there is 'fluid' in the cavities in the unit that houses the cassette. Has anyone else experienced this problem? Any advice would be much appreciated. Most but not all of the fluid had successfully reached the container. This has happened before so I checked the operation of the unit to the best of my ability and the blade that controls the discharge was opening fully and it seemed that the discharge was going directly into the container. Not sure if this problem has occurred whilst static or whilst driving (unable to empty tank)
Cheers, Rob.

I had this on one occasion, turned out that there was some flush water left in the bottom of the bowl when I removed the cassette for emptying.  I now always double check the bowl before removing the cassette.


I would eliminate any possibility that this happened before going too far looking for problems with the toilet.

Hi Rob, yes, we had that problem with our old 1995 Exec.

The answer is a new cassette lip seal, to prevent the waste escaping over the top of the cassette, and making sure that the cassette flap is open before doing any 'business' in there.

Depends which toilet/cassette it is, but here's a page of them from ebay:

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Slaphead beat me to it.

Before removing the cassette, always open the valve and let it drain for a few moments. Then close the valve firmly (or you will be in even more trouble) and there should be no fluid on the top.

The rubber seal on top of the cassette simply presses against the underside of the toilet bowl. If there's any fluid sitting at the bottom of the bowl when the cassette is slid out it will spill all over the place as you described.

Do make sure that when travelling the flap is FULLY closed.  It flaps across, looking closed but the last little bit of the lever travel LIFTS the flap a fraction to bring it hard against the seal.  If it does not lift thaen there is a possibility of splash, paticularly with an old seal.

Thanks everyone for the rapid responses and advice. Will check everything that you say and let you know. I am skeptical that the spillage is from remnants in the bowl as the amount (and type !) of spillage suggests it had already been flushed. But could be leaking if nor shut properly before travelling / could be faulty seal.
Cheers, Rob

I would empty it, then half re fill with clean water, dry the outside, then give a good shake about and see if any escapes, hold it at slight angles. You'll likely have some small amounts escaping, there is a seal at the blade opener number 13 on diagram. I have found this to clog up sometimes, and a good clean can can stop the seepage. the actual blade can be cleaned also as this sometimes leaks slightly. The age though might point to something more, or more seals leaking than the one. The water test usually works for me

I wonder if you still have the original cassette. If so I'd recommend a new one, they're less than £100 on ebay, and you usually get a new toilet seat and fluid in the refresher kit. I went down the route of replacing the main seal on my 10 year old cassette, and a few months later the seal on the pressure relief valve stared to leak, I also noticed a slight weep on the blade opening lever O-ring when I gave it the shake test. Replacing the whole thing was the sensible option.
Al.

Most of the newer ones in the 'refresh kit' mentioned above also now have built-in wheels which makes emptying easier.

This is all really helpful.  The same thing happened to my toilet cassette on my last trip.  I have noted all the posts and will make sure all in place for my next trip!  My cassette seems quite new so I don't think it is a problem with the seal (van 5 year's old)
Thanks
Lizzie

This is the crucial bit Nessie. It catches out loads of people until they realise exactly how the system works. I was a bit too "concise" in my earlier post.

"Before removing the cassette, always open the valve and let it drain for a few moments. Then close the valve firmly (or you will be in even more trouble) and there should be no fluid on the top."

When you have taken the cassette out, go back inside the van and look down the loo bowl. You will see clear to the bottom of the housing.

"The rubber seal on top of the cassette simply presses against the underside of the toilet bowl. If there's any fluid sitting at the bottom of the bowl when the cassette is slid out it will spill all over the place as you described."

Hope this helps

Great, thanks Dave

Gromit wrote:This is the crucial bit Nessie. It catches out loads of people until they realise exactly how the system works. I was a bit too "concise" in my earlier post.

"Before removing the cassette, always open the valve and let it drain for a few moments. Then close the valve firmly (or you will be in even more trouble) and there should be no fluid on the top."

When you have taken the cassette out, go back inside the van and look down the loo bowl. You will see clear to the bottom of the housing.

"The rubber seal on top of the cassette simply presses against the underside of the toilet bowl. If there's any fluid sitting at the bottom of the bowl when the cassette is slid out it will spill all over the place as you described."

Hope this helps

I'm still convinced that Nessie's problem is the seal Dave.

He says that there's 'fluid' in the bottom of the compartment and his coy description of the 'fluid' sounds like it isn't of the flush water variety.

There's only one way that human fluids rather than flush water can get into the bottom of the toilet compartment, and that's over the top of a leaking lip seal.

If the 'business' is done with the flap closed and the seal is leaking, then a significant amount of fluid will escape over the top of the cassette and into the compartment recesses.
The important point is that it will build up and not be noticed until you empty the cassette, so small leakages over say two or three days of use will contribute to the quantity of fluid in the bottom.
If, OTOH, it was just the remaining flush water that accumulates after you've closed the flap, it would only spill out once as you remove the cassette, and it wouldn't smell or look like his description.

IMHO, of course.

I have the same problem and after some experimenting, some of which has been mentioned above, I have concluded that it is the main lip seal on the top of the cassette, which, when the cassette is in situ, presses against the underside of the toilet bowl.  (as Gromit states above)      I proved it by sliding the cassette in place, and then I placed two wedges under the cassette, pushing it up tighter against the underside of the bowl.    Cured !       I also noted that the square sliding plate which slides over the lip seal when you withdraw the cassette, was very loose, indicating again the at the lip seal needs replacing..       Genuine Thetford £14.95 or repro at £8.99.    There are numerous posts about how to replace it  ... pretty straight forward.

Bob

I've overlapped MeanChris's post  -  but the same conclusion

The sliding plate that covers the seal when you remove the cassette is there to trap any fluid dregs that may still be in the bowl. As has been said, a loose plate usually points to a worn out seal.
Al.

BobK wrote:I have the same problem and after some experimenting, some of which has been mentioned above, I have concluded that it is the main lip seal on the top of the cassette, which, when the cassette is in situ, presses against the underside of the toilet bowl.  (as Gromit states above)      I proved it by sliding the cassette in place, and then I placed two wedges under the cassette, pushing it up tighter against the underside of the bowl.    Cured !       I also noted that the square sliding plate which slides over the lip seal when you withdraw the cassette, was very loose, indicating again the at the lip seal needs replacing..       Genuine Thetford £14.95 or repro at £8.99.    There are numerous posts about how to replace it  ... pretty straight forward.

Bob

I've overlapped MeanChris's post  -  but the same conclusion

I found out during our first overseas trip in our first 1995 Executive, that SWMBO had been using the toilet with the flap closed as she was used to seeing water in a domestic toilet bowl.

The first emptying of the cassette on a French site was something of an embarrassing revelation, as all the compartments below the cassette were completely full.

A change of habit to using the bowl dry with the flap open was enough to reduce the problem until I could get hold of a new seal. I did learn during this trip to make sure that the residual flush water is (EDIT) completely gone, as it's enough to spill over the leaking seal if you don't leave the flap open for about 30secs after flushing, to allow it to drain out of the bowl completely before closing the flap.

Can't argue with any of those comments. 

If Nessie cleans everything up and dries the bottom compartment thoroughly, he can do a trial run using flush water for a few simulated toilet visits, then follow the patent instructions before emptying his cassette.

If the bottom compartment is wet, I would agree that he needs a new seal. If there's no water in there it was operator error.

Either way it should tell him where the problem lies.


It is just possible that a previous owner has tried to remove or replace the cassette with the flap open!!!! and got it thoroughly stuck. Wrenching it loose could have misaligned the whole unit, in which case a complete replacement might be the only answer. Speculation again of course, but remote advice is always problematic.

Thanks again for all the recent advice. So here is where I am at the moment. Just to be clear the leakage was 'waste' and not flush water - so assumed to be coming back up from the tank. I have fitted a new waste tank seal and sprayed this and the cap seal with Thetford Seal lubricant. I have given it a thorough shake test - and there is no apparent leakage. The maintenance instructions also say that the automatic pressure release vent seal should be cleaned and lubricated. Please can someone tell me how to access this? I will do that, refit to the van and see what happens. Will for sure let you know. Cheers, Rob

Forgot to mention that I will for sure just get a complete replacement if I have further problems. Cheers, Rob

Details on service replacement of valve, here. [You must be registered and logged in to see this link.]

Thanks for that Peter

Mine leaks a bit when the cassette is turned upside down and shaken gently during rinsing. I tried to unscrew it but it doesn't want to move - but now I know that it should unscrew I'll give it a bit more welly.

Rob. Don't shake too hard. There are components inside the cassette that can be broken if you are too vigorous.