Despite what some may say, Thor is one of best with diagrams etc for things like this. Each coach can be different even within a same model. Strongly suggest getting the plumbing diagram, and post picture of any question if concern is not resolved.
i.e. I had brand new coach and Dealer and I clashed because I could not get my fresh water tank drain valve to drain. They insisted I was turning the wrong thing !!!!
Turns out my model's drain valve will not work unless water pump is "on"
The owner's manual that came with the coach was NOT for my serial number.
Mfg sent me plumbing diagram and new customized owners manual for my coach. I thought the pump was odd at first but actually it pumps it out very fast. My overflow line runs from top of tank to rear of coach. When it is full I can see water coming out the back and I turn off the hose. Eeasie Peasie