that is interesting! a good way to keep a good water level for sure.
since our kitchen is in the rear and the bath is in the middle, we have two seperate gray tanks, i personally wish they'd just put a bigger black tank in the middle for all of it. like you said, better way to keep a good water level in the black tank.
so after reading through this thread, and having to deal with a similar situation that the PO left the TT in, mines sitting outside now full of water and ridex. probably wait till saturday or sunday to hook it up to the clean out on the sewer line and dump it. might just do it twice, i really need to get that clear 3" extension so i can be sure when i'm 'runnin clean'