Frank is right on. After using the clear elbow with our camper, I see why I was always in the penalty box for dumping the black tank when we used to rent a TT before we bought.
Without that adapter you don't even know if it is actually empty or if you have a blockage that is preventing a full dump. The idiot lights are NO HELP since they can indicate "full" for a LONG TIME after you dumped due to crud on the tank walls.
Always dump from Black FIRST (then turbo flush till it runs clear); THEN dump gray water. That way you get to flush out your hose with soapy water before you put it away.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW