Thetford cassette vent seal, part number 20339.
The vent seal is found on your caravans cassette toilet holiding tank, please be aware that thetford have used more than one vent seal so if you are not sure if this is the correct part please refer to your toilet manual where the part numbers should be listed.
The use of domestic household cleaners can have a detrimental effect on the seals in your cassette toilet. Thetford make a range for 'seal safe' clears and lubricants that should be used.
