Question

Hi. I have a Thetford Cassette toilet in my Avondale Mayfly caravan. I think it might be a C2 model but I'm not sure. Perhaps you could advise me what the Mayfly was built with. Anyway, on the holding tank just by the switch (yellow top) that controls the opening of the flap there is a hole. On your download Thetford C2 C3 + C4 Holding Tank page (exploded parts) this hole is numbered #18 but it doesn't say what it's for. The hole on my tank is open and if I pick the (full) tank up vertically to go and empty it, the contents come out of this hole! Is there a bung of some sort that should be in this hole? If so, do you have one? Regards, LM.

Answer

This hole is relevant to the older tanks and this hole is sealed by the vent seal, our ref. 129417. The hole is sealed by the float mechanism making contact with the vent seal and if fluid is coming out of the hole then the vent seal or the float may be missing from your tank. This is not a satisfactory arrangement and later tanks have a different design.