[Lynn Eades]

Hi Mike. I don't think the seal is supposed to seal on the shaft. The rubber end seals in the impellor and the carbon runs inside the pump housing. A successful seal at these two places prevents water getting to the shaft. As long as the assembled length has enough spring tension, it should be fine. I'm having trouble understanding where the problem is? Can you expand?
It is known that this old design has trouble holding water when used in conjunction with a pressure system. Having said that, I run a 4 lb system (Morris Minor cap) with no problems on these standard type pumps.