Last week when Keith was emptying our Thetford Cassette at the campsite, he accidentally dropped the measuring cup down the chemical disposal point!! and neither one of us was gonna try to retrieve it. He had also noticed the seal had a small leak when he turned the cassette on its side.

So, when we got home, I went on line to order up a new measuring cup and a new Lip Seal (23721). While doing this I was skimming down the other spare parts and came across a 'Slide Cover 21333'...and didn't know what this was.
http://www.thecaravanshop.co.uk/popular-...3/prod_814.html

We have had the van now 2 years and in all that time we have not had a slide cover on the cassette loo. We then went into looking at You Tube videos on the Thetford loo and realised the Lip Seal had never been fitted properly, and we had never used any seal Lubricant....still on that learning curve!!

But what we are not sure about is a) Do we need a Slide Cover as never had one for 2 years. and b) If we should have one, do you leave the sliding cover closed when you slide the cassette into the van or remove the cover?

Chris...

You need it closed when sliding back, it has a small triangle mark on slider which should line up with another triangle on the main cassette . Paul.

Putting the cassette back in causes the slider to open.
On more recent models the sliding cover is used as a lever to open the seal for maintainance

The cover opens and closes as you pull/push the cassette in/out. The lever in the toilet closes to form a seal when using the Eriab and the cover closes when you pull the cassette out to form a seal for you to empty it.

https://www.youtube.com/watch?v=gAoQecdnp3s

The above link shows the sliding seal, and is quite good for maintenance.

I think it would be wise to use gloves