When I first got the rig I thought seriously about installing one. After much research, and on the advice of several long time RV'ers I decided why bother?
It's a black tank...I don't need it to be sanitized. Just add a few gallons of water after every dump, use plenty of water when flushing, and let it get rather full-ish before dumping whenever possible.
I will dump a little soap in there once in a while just to slippery things up a bit.... but I really don't see this as necessary.
Once in a while in the past, when I'm at home and not holding up anyone at the dump station line... I have occasionally refilled the tank with fresh water and dumped once or twice to give it a bit of a wash out.... but logically I realize it's a waste of water and don't do this much any longer...
__________________
|