We stay most of the winter in a campground with low water pressure and routinely run the pump together with the campground water. The check valve in the city water input prevents any back feed into the campground. The pump will cycle on when the park pressure is lower than the pump pressure and off when it isn't.
I fill the tank about half full so I can add fresh water every two weeks or so. The water comes from a well and is not chlorinated so I don't want to leave unused water in the tank too long.
Clay WA5NMR - Ex Snowbird - 1 year, Ex Full timer for 11 years - 2004 Winnebago Sightseer 35N Workhorse chassis. Honda Accord toad.