Engineer Mike, and everyone else, I should reiterate on a couple of things. I do not trust the gravity-fed system. For the first two years of ownership I had the reservoir full, and it hardly went down at any time except probably through evaporation. I drain the reservoir when I winterize the coach. After reading various input about overflow problems with too much water, I decided to try the squeeze bulb. When I saw that I was able to put in a half gallon of water I knew the gravity system did not work. I leave the small flow valve off except when using the squeeze bulb, which I will use again before i winterize this December.
St. Louis, MO
2007 Limited SE 36FDTS