do you keep water in holding tank between trips?

I keep ours filled all the time. When we come back from a trip, I drain out the partial tank of campground water and fill it up with city water til the next trip. The chlorine keeps the system sanitary and I always have water in case I need it. If it sits more than two or three weeks, I change it before leaving on the next trip. Some of the State Parks we go to have so much chlorine in the campground water it's tough to get it past your nose.