You should
never leave the black water valve open, or you definitely will get sewer gas/odors inside the RV. You'll also get much better emptying by letting the tank fill and only emptying it when it is nearly full, but definitely empty it before leaving the last campground of your trip.
Similarly with the grey tank. Personally, I leave it closed until it needs emptying, and you want to use the grey water to flush the sewer hose after you empty the black tank. It is possible to leave it open if you form a trap in the sewer hose to keep fumes from entering the RV.
And lastly, if you leave both valves open at the same time, you risk having 💩 backfilling into your grey tank.
Thor Forums
