I have never seen it to be much of a problem since you keep the black tank valve closed anyway until time to dump. Even the small (12 gal) tanks in the 276 and 296 can go an entire weekend, or longer by keeping the flushing to a minimum. When time to dump, close the valve on the gray tank, remove it's hose from the sewer connection, and hook up your sewer hose for the black tank and dump. For the gray, I use the Valterra T01-0091VP previously mentioned, a regular garden hose, and a Camco 39322 3/4" hose to 3" sewer adapter.
Bob & Doris
2009 Toyota Tundra CrewMax 4x4 - 5.7L - 6 Speed Auto - 4.30:1
2013 Rockwood HW296