It boggles the mind how an assembly line could make a mistake like that and makes you wonder how many other Thor coaches from that plant have the same mistake.
Whether it's done under warranty or you take it upon yourself to fix it I agree the only correct fix is to just install a new flusher into the black tanks and leave the incorrect one in place.
Ted & Melinda
2016 ACE 27.1
2016 Chevy Sonic Toad