I have a W&C HeadMate which was, I believe, factory installed. I've rebuilt the pump, and am about to re-attach it. The flapper valve is at the point where the pump assembly attaches to the base. Do I need to use some sort of sealant on the valve or the housing when I re-attach? There was no gasket when I removed the pump assembly, but I'd hate to get those almost-impossible-to-reach screws back in and the have to pull the whole thing off again because it's leaking.