We have a Thetford cassette toilet in the caravan and the black disc that opens and shuts is not opening but it's letting liquid into the cassette, but will not seal Back up.

SOURCE: Recently purchased a caravan with a thetford c-200

you may have this already but try

http://www.thetford-europe.com/web/show/id=51498/langid=42

Bruce McLeod

• 67 Answers
• Posted on May 01, 2009

SOURCE: freezer door not sealing

replace the seals and / or have the hinge adjusted

SOURCE: how do we empty and maintain our thetford porta

Go to www.thetford.com.
Click Customer Support then Product manuals and download manual in PDF format.

SOURCE: Hi, have a built in thetford toilet in my caravan.

Don't send money. Just go to thetford.com and download info.
Some tips - if seal is old and breaking up make sure you recover all the bits which have fallen into the flush water tank. If new o-ring seal not available use outdoor silicone sealant and allow to set for 48 hours before adding anything other than a small amount of water to test flush action. Electric circuit includes a fuse and microswitch which are both contained within the flush water tank but you are unlikely to have problems with these items.

SOURCE: I have a thetford toilet in my caravan and cant

Here is a link for the Manual for your model http://www.thetford.com/HOME/PARTS/PortableToilets/PortaPotti365PDFs/tabid/669/Default.aspx