how can i get to the intake or rinser leak behind the to of the thetford?

Is it a secret as to the model? It's like saying 'My car wont start' but not telling anyone what car it is.

If you said what model then someone may have had the problem and tell you. Meantime contact www.thetford.com select parts and select permanent toilets on dropdown menu
Select your model and the parts exploded veiw will show. below is the parts listing numbering and naming all part. You may be able to see where it is from that.
Failing that email thetford. slecting 'Customer Support' Don't hold your breath as they are not that quick replying.

Nobby
September 2008