Thor Compass extra valves mystery?

[JKConey]

There are 2 nondescript pull valves above the black and gray dump release ones. This coach has one black tank and 2 gray tanks indicated on the display panel. The dealer, and the Thor tech I've been corresponding with, can't tell me exactly what each is for? I was told the shower water goes into the black tank, so why the need for 2 gray tanks? How do they operate? Of course this coach has no dedicated manual, so everything is a challenge to figure out. Anyone?

[JamieGeek]

Ask Thor to send you the plumbing diagrams for your coach (both waste and fresh). That should answer your questions.

Our old 5er had two grey tanks: One for the bathroom sink and shower and one for the kitchen sink.

[EA37TS]

On my Challenger I also have 2 gray tanks and one black. Everything on the passenger's side (shower, outdoor kitchen sink and washing machine drain) dump into the rear gray tank. Everything on the driver's side (kitchen and bathroom sink) dump into the forward gray tank. The toilet is the only thing that dumps into my black tank.

I had the same issue where neither the Thor regional sales rep nor my dealer could tell me how the tanks were plumbed. I figured it out by running a fixture and then dumping a tank. I repeated this until I knew which tank each fixture dumped into. This was later confirmed after I received the waste water diagrams from Thor.