Adding water after dumping black tank

Valterra makes a "Flush King" that hooks to the sewer discharge before you attach the hose. It is clear plastic (so you can see when the rinse water is clean) and has a garden hose attachment point. Using this allows you to backflush the tank and add water to it without having to run a hose inside the RV. I use it even though the trailer I have now has a rinse system, because it lets me see how clean the rinse water is. I got mine from Camping World. It's sort of expensive, but it is worth it to me to know when the black tank is clean.