Camco 39052 RV Holding Tank MaximizerCamco Grey Water Holding Tank Maximizer allows you to route grey water to your black water tank, so you can camp longer before emptying your tanks. Typically, your grey water tank fills up faster than your black water tank, so this reduces your number of trips to the dump station. The Maximizer can also be used to rinse your emptied black water tank by routing grey water into it. The emptying grey water will help rinse out your black water tank.