I recently bought a 2015 Pleasure Way Excell. It was used. All works except for the fresh water system. It was delivered to me with a full fresh water tank and maybe that should have been a clue. I used only the fresh water tank on my maiden 2 day camping trip. I didn't want to carry that much water. Next time out and I'm still out, I hooked the camp water to the fresh water intake and thought all was ok until.i saw water pouring out of the fresh water tank overflow. I had to stop using direct water feed and work through the tanks. Is there a valve that camp water should close to avoid interaction with fresh water tank? Thanks if you can help. Bob