Filling fresh water tank?

We have water in the RV, the pump kicks on, but board still says the tank is empty. I found inside the hot water compartment two valves to empty the fresh water tank and the hot water tank I believe. There seems to be no over flow for the frest water as the hose has now been hooked up for about 2 hours and no over flow. No idea if I have a full tank of fresh water or not, or if the pump is just picking up some water that is in the pipes or what. The Motorhome has the quick fill system. Staight up for city water and then turned sideways for fresh water tank. We have been under the MH and see one large tank, so we are thinking is this divided inside the tank into three? If so then we are looking at some small tanks.