So there has been a horrible smell in my bathroom. The seal on the bottom is good, holds water. Then I realized the obvious problem---underneath the water spray valve there is a manufactured hole that leads directly to the black tank! Why is this here? Am I missing something that is supposed to close this hole? I've been having flies come directly into my coach from the black tank through this hole! What the hell??
Since that Thetford link doesn't show the part. on the list it is #6. There should be an 'S' shaped piece of hose connected to make a water trap. It is actually an overflow for the bowl. Every time you flush, a small bit of water should enter to keep the trap full. Art