I have an '08 Adventurer 38J that has a slow leak (pinhole) at the joint between the black tank and the 3" drain pipe coming out of the tank. The pinhole is in what looks like a clear silicone but I have been told it is a product of plastic welding the drain pipe to the tank. It is under warranty but I am 400 miles to the nearest dealer. Winnebago is not sure about anything to seal it, and a dealer told me to use Dicor (roof sealant) since that is what they will try if I bring it in for warranty. Anyone have this problem? Is the drain pipe threaded into the tank?