Thetford Cassette

I found the Thetford site showing info on parts & repairs

Site Link

I am still interested in hearing if others have had this problem and whether it was fixed.

Mick, it's abit of a mystery if it works fine when it's removed, however I did have the same issue with mine.

If you have already lubricated the flap then try removing the entire mechanism by twisting the round hatch with your thumbs. There are some alignment marks as a guide. Remove it from the cassette and you can inspect all the moving parts.

I found that part of the mechanism, fully visible when removed, had slipped up over another part and was preventing full movement. It had actually slipped over the other part BECAUSE of my vigorous use of the flushing lever so you may find the same. I sorted that out and it was fine.

Lubricate the seal when re-installing.

Hi Mick and Vicki. Our tank developed the same problem earlier this year. I think our problem was because of the buildup of crystalisation on the actual mechanism from the waste. And our cassette is 5 years old...A long time for it to build up.
I had actually dropped the cassette on its' corner one day when carrying it to be emptied, and this seemed to dislodge something causing the whole round disc and arm which operates it to swing around inside when I tried to close the thing. Consequently I bought a whole new cassette thinking the old one was "cactus". Well, before the new cassette arrived in the mail, the old one suddenly went :clack" one day and a great big bit of crystallised "stuff" fell off the arm and it has been fine ever since! Maybe you have some of the same problem?
Incidently, since I have started to use the "Napisan Method" in the cassette and the top tank, I have had nearly zero smell even after a whole week here in the warmer northern climates...I can say it seems to work an absolute treat plus I reckon it will de scale the tank in time.
Regards, Jan O

Best way to clean the encrusted crud is to mix a strong dose of any Nappisan 'home brand' version - two table spoonfuls in a litre of warm water and stir well. Add dissolved mixture to the cassete tank (fill right up) and shake it around just to mix. leave it for as long as possible - 24 hrs works well. Empty and flush well then lubricate parts with olive oil

Cheers John

Hi Mick,

Must say great looking set up as we walk past in an evening admiring it while you are at Glenelg, one day.........when the kids leave home.(a while yet at 3&5)

We don't have BT but an Expanda and have found the use of olive oil on the seal as well as a few drops inside the cassette mechanism makes the operating lever very smooth, not sure whether this will help or not for your issue.

Cheers

Christian