Newbie and a 2002 keystone cougar

babun wrote:
Thanks, I was thinking also, that I could leave both open-grey and galley, because of the hard pipe.
Shouldn't get any back flow of smells, right? There should be Ptraps on both inside the TT.

Some folks say they get smells from the sewer, if they leave the valves open. Some say bugs can crawl up. I think there are too many variables to really know if you will. It's the kind of thing you can just try, and if it is unpleasant, change. There are traps on all your gray/galley fixtures. But odors might still come from the vents on the roof, and waft down through your windows/doors. And some campground systems are more gassy than others. As I said, just too many variables to know. The convenience of uninterrupted showers should be worth the time it takes to try it and see.

Thanks, I was thinking also, that I could leave both open-grey and galley, because of the hard pipe.
Shouldn't get any back flow of smells, right? There should be Ptraps on both inside the TT.

Since you are setup with hard piping, the only tank I would leave closed until near full, is the black tank. Rinsing a slinky won't be an issue, since you are hard plumbed. But you don't want a poop pyramid to build up in the black tank, so you want to retain all the liquid until nearly full. Then dump and rinse well, then close the black valve for next time. Buildup in galley and gray tanks should not be an issue, but it wouldn't hurt to let them fill before draining once every few months. The turbulence of a full tank dump can help flush food and hair.

A lot of trailer floor plans have a 2nd grey or what they call a galley tank. I leave mine ( it is a 35 gal tank) closed until it gets full to help minimize stuff getting stuck on the bottom of the tank. I would think food particles and possible grease laying on the bottom would lay there when no water is flowing. I leave my grey tank open until the last day then I close it to use for flushing the hose after black tank is drained. This is just how I do mine as others might do it differently. Happy Camping.