I have just bought a 2000 Herald Clermont. The dealer gave us as part of our starter pack a length of black waste pipe which he assured us was the correct size to fit the waste outlets. After siting the van for the first time, the black waste pipes would not fit the outlet points. We went back and the dealer gave us a length of a larger size, which was way too big. Has the waste pipe standard changed recently? Any suggestions as to why the pipe doesn't fit?