Thetford Cassette

Submitted: Thursday, Apr 16, 2009 at 21:43
ThreadID: 125562 Views:4044 Replies:5 FollowUps:3
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G'day all,

I have a question regarding the Thetford cassette, in particular the opening flap that seperates the flush tank from the holding tank. Ours appears to be not opening fully when the round handle is turned, it would appear to open 90% but if it's open & closed with a bit of vigour then you can get it to fully open.

Our original Thetford had a fault from new where it would only open 50 - 60% and BT replaced it early on, just wondering if this is going the same way or any adjustments can be made, it appears to be the turning mechanism is the problem

I have flushed and cleaned & cleaned & flushed, Also when the holding tank is removed the turning mechanism on the holding tank works fine.

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Reply By: NIK `N` OFF - Thursday, Apr 16, 2009 at 21:57

Thursday, Apr 16, 2009 at 21:57
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.
AnswerID: 577542

Reply By: Gone Bush - Thursday, Apr 16, 2009 at 22:19

Thursday, Apr 16, 2009 at 22:19
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.

AnswerID: 577543

Follow Up By: NIK `N` OFF - Friday, Apr 17, 2009 at 02:04

Friday, Apr 17, 2009 at 02:04
G'day Stephen,

I found the Thetford web site with a break down of photo's and parts that explains how to do just about everything on the cassette, good for future reference.

Site Link

I ended up spraying the turning mechanism with some lanolin spray and it appears to be working ok now.

I have always as part of maintainance given the rubber seal a smear with olive oil.

Hope all is well back in your neck of the woods
FollowupID: 851104

Follow Up By: Turist - Friday, Apr 17, 2009 at 02:26

Friday, Apr 17, 2009 at 02:26
G'Day Mick

You will find most of that information loaded in our File Swap section.

"Do It While You Can"
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FollowupID: 851105

Reply By: Rockgoc - Friday, Apr 17, 2009 at 00:31

Friday, Apr 17, 2009 at 00:31
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
AnswerID: 577544

Reply By: Grumblebum & Dragon - Friday, Apr 17, 2009 at 04:29

Friday, Apr 17, 2009 at 04:29
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
AnswerID: 577545

Reply By: TW - Friday, Apr 17, 2009 at 16:43

Friday, Apr 17, 2009 at 16:43
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.


AnswerID: 577546

Follow Up By: NIK `N` OFF - Friday, Apr 17, 2009 at 19:08

Friday, Apr 17, 2009 at 19:08
G'day Christian,

Small World huh, well don't be a stranger mate, next time your wandering by say g'day.

Your tip of olive oil is noted, we have been doing that since day one on the rubber seal, yesterday i gave the underneath of the slide section a good smear with olive oil and that seems to have cured the problem.

FollowupID: 851106

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