So, initially, I noticed I had water pooling in the storage compartment behind the passengers side rear wheel. Tracing the "drip", it was coming from the floor cut out where two white PEX pipes go in & out (to the San-T-Flush check valve, then on to the black tank).
Thought I had it fixed ... as after going inside, I found where the factory stapled right through a supply line going to the bathroom sink. I replaced the supply line, which required removing the entire "night stand" cabinet beside the master bed. Was sure I had the leak licked then, but no dice - still dripping water.
Tracing some more, the two PEX pipes leading to this San-T-Flush Check Valve were wet. The Thor "schematic details" state that "... check valve in walls between bath and bedroom with access panel in left shirt closet ... panel must be removable with screws".
I see no such access panel. What is recommended to gain access to this check valve??? I’d like to make sure there's no access before I cut the wall open. ~sigh