Covered in post 4. The big concern here is coaches without a gravity fill. They have to have vents that drain water fast enough to prevent tank pressure build up in an overfill situation. Had a custy with one such coach. 4x6 foot flat tank 6" thick under the floor. Had vents on each side that would leak on cornering. So, he put drain valves in them. Put the hose on the female threaded fill and turned it on, thinking it was the city water inlet. Turned the water tank into a 9000 lb jack on the living room floor...it went down to the axles and up from there.