Hi, I'm brand new to this sight and only in my second season with the van so need some help please. I have a Bailey Senator California van fitted with a Thetform electric flush toilet with manual sluice, as there probably is in many many other types and makes of van. Cleaned and correct chemical/water levels put back after each empty. Within the last few days I/we/the wife, have noticed unpleasant and unwanted odours, emanating we believe, from the toilet. Not a pleasant subject I must admit but, as you look down into the toilet there is what looks like a rubber disc/flange which opens to allow the pan contents to drop into the tank when the sluice handle is operated. After a couple of sluice/flush cycles and with the flange in the closed position I have purposely put some flush back in the pan, which initially stays put, but within 10 to 15 minutes it has drained into the tank which would indicate a close but not tightish fit. Is this normal or does this flange deteriorate over the years. If so, can it be replaced. Our van is 2009.