Clay L wrote:
There are usually air admittance valves on the kitchen and bathroom sinks. It comes off a stub on the sewer side of the traps. It has a flap that opens when the gray water is dumped so water is not sucked out of the traps. If the flap does not close properly odor can escape the gray tank. That might be where the odor is coming from.
The air admittance valves usually can be unscrewed by hand. Replacements can be obtained many hardware stores
Thanks & interesting. My rear bathroom's sink goes directly to my second black tank. We get a terrible odor in there from time to time (literally always have from when the camper was very new). I have seen this valve, but didn't know how it worked.
I think I'll investigate that a bit further. :)