Fixing a blade on Thetford Toilet Cassette

Submitted: Saturday, Jun 19, 2010 at 17:14
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The blade that seals the holding tank on our Thetford 402c Toilet Cassette will not open can anybody help with a fix.
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Reply By: Boystoy - Sunday, Jun 20, 2010 at 03:55

Sunday, Jun 20, 2010 at 03:55
Hi Brian,

When you take the tank out, can you operate the blade manually? This would be the first check.
If this is OK, then if the opening knob rotates, then some of the linkages between the knob & the tank have come off or are very loose. (bugger to get at!!)
If you download the BOG Bible, there is a deal of info in the 'Thetford' tab. (Not necessarily exactly what you need, but info to steer you in the right direction.)
One problem that you may have, is lubrication of the seal. You will need to remove the screws that hold the cover down to remove the seal rubber. Give this a good clean, then lubricate it thoroughly with olive oil & re-assemble. A good idea if you haven't done this before to mark everything with a textra before dismantling, to make sure it goes back the same way.

Good luck

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AnswerID: 580655

Reply By: Motherhen & Rooster - Sunday, Jun 20, 2010 at 07:55

Sunday, Jun 20, 2010 at 07:55
Hi Brian

Has the cassette slipped out of alignment a little? In this case it will work perfectly when the cassette is removed, or given a gentle shove into it's correct place. Always seems to happen on a wet night when you are camped on Qld black clay.

It can also jam if the seal has not been opened for some time, in which case take the cassette out and use as much friendly persuasion as it takes to unstick it.

These are the only issues we have had with ours.



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AnswerID: 580656

Reply By: Itldoo - Monday, Jun 21, 2010 at 00:29

Monday, Jun 21, 2010 at 00:29
Hi Brian,
Probably the same problem that I have. Take the tank out. If still not working take the 8 screws out and lift off seal. Need to clean the tank as you have to pull the round plate. off by pulling the shaft out and repositioning the sliding mechanism. Then put the round plate back into position.This always works for me. Hope this helps.
AnswerID: 580657

Reply By: Bushtucker Man - Monday, Jun 21, 2010 at 06:03

Monday, Jun 21, 2010 at 06:03
We had a problem with ours after returning from Tassie so I put 2 teaspoons of citric acid in the tank, then about 10 litres of water turned the tank upside down and left it for 24 hours. During that time I shook the tank a few times to stir up the contents, then after emptying flushed it with clean water and hey presto it worked also no sign of calcium buildup. A spray with olive oil and it works better than new.

AnswerID: 580658

Reply By: Tellem Bugrem - Monday, Jun 28, 2010 at 22:47

Monday, Jun 28, 2010 at 22:47
There was an article on
dated 19.01.05 - "Fixing a Stuck Blade on Thetfor Cassettes"

Don't know if it is still accessible.

I have a copy which I could scan and email if anyone is interested.

AnswerID: 580659

Reply By: Tellem Bugrem - Friday, Jul 02, 2010 at 01:58

Friday, Jul 02, 2010 at 01:58
Whilst sitting on the dunny.......

I have just done a spring clean of our C2 Thetford Cassette.

1. Cleaning of the flap and rubber seal is fairly easy. Remove the plastic sliding door and wash everything you can see with hot sudsy water. Remove the eight stainless steel screws and lift assembly off. You can now remove the rubber seal for cleaning, drying and coating with olive oil. I had considerable calcium crust buiuld up on the blade, and with the aid of a fine brass wire brush, D-solv-it, soapy water and elbow grease, it now looks like new after a smear of olive oil.

2. The valve shown in the photo must be turned to the position shown before it can be gently levered up with a flat screw driver.Image Could Not Be Found. (line up the edge of the turning knob with the bottom right screw of the flap lid housing.)
Don't try prising it out with the screw driver into the side of the turn knob. It will break the thin plastic. Use a fine flat (electicians) screw driver to gently prise from where the valve housing goes into the cassette top.

When removed you can gently take off the soft circular pad, and whilst holding the valve button down, you can twist and turn the white plastic disc for removal. This frees the rubber ring. Clean everything, coat the rubber ring with olive oil and re-assemble.

3. The air release valve can be removed in a similar way to the previous one. You must line up the the edges of the knob with the end of the flap knob as shown. Then gently prise the unit out. Clean and oil the O'ring and then re-assemble.
Image Could Not Be Found

4. The water spout can be gently prised out from the position shown. Again clean everything in sight, Gently remove the O-ring, clean, oil and replace.
Image Could Not Be Found
This 2002 model looks brand new!!


AnswerID: 580660

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