[jimcol]

An alternative to closing all valves, just put a drip loop in your sewer line. Works like a p-trap does under your sinks. I've used rocks or boards to create such a trap. About a foot from where my sewer hose hits the ground coming off the 5'er discharge pipe, I place a rock or board about 4" high. Whenever wastewater is discharged from the RV the loop created will stay full of water preventing sewer gases from coming back up the pipe into the holding tanks. Many of these RV Parks create quite an odor if too many people decide to dump tanks at the same time.