Dumping at Campgrounds and Flushing Black Water Tank Too

We do as most above--dump black, then grey. Why not have some water in gallons to dump in with treatment, then before setting up on next trip, dump if not FHU. This gives the water a chance to slosh around and clean things. Before we store for the winter, we do complete water fill with calgon/soap, drive around a bit, go to the state park for $3 and do a full dump before winterizing.