Join Date: Jun 2016
Location: Orange County, CA
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
I have a transfer pump to move excess gray water into the poo tank if needed. It's a cheapo Harbor Fright impeller-type utility pump, fed by a separate 3/4" hose from the gray tank through a ball valve. It pumps gray water up to an inlet in the top of the poo tank directly above its 3" drain to the dump valve - the theory (but I've not tested it yet) is if there were a Mound Of Doom partially blocking the poo tank's drain, it may help to blast it clear. Obviously there's a check valve to absolutely prevent any poo tank contents from backflowing towards the pump, but I don't think it would ever happen anyway. I put the 3/4" outlet on the gray tank about an inch off the bottom, to prevent too much "solids" there from being sucked into the pump.