We are full timers and exclusively use our fresh water tank. We turn off the water pump and the water heater whenever we leave the RV even if it is only for a short time. We also leave our waste tanks closed. An example, our neighbor left his water on , flushing his black tank with the valve closed (a big no no that lots of RVers do). We looked out and saw water pouring out from underneath is trailer. Fortunately, we caught it before it came inside his trailer. Another good reason to turn off your water every time you leave.