Sanitize the white water tank by draining it and then filling it halfway. Add 1/4 cup household bleach for every 15 gallons of capacity in your tank. Run cold water through all of the faucets and then run hot water to get the bleach into the hot water tank.
Let the water stand for six hours and then drain the system. Add 1/4 cup baking soda to a gallon of water and pour it into the white-water tank. Fill the tank and then open all the faucets to remove any traces of bleach. Drain the tank and then fill with fresh water.
Allow the black water tank to fill two-thirds full to prevent solids from accumulating under the toilet. Follow your RV manufacturer's instructions for emptying the black water tank at a campground or truck stop dump station.
Purchase a rinse wand. The wand attaches to a hose and enters the black water tank through the toilet. Clean water rinses the tank as it is flushed through the wand, preventing waste from building up on the bottom of the tank.
Treat the black water tank with a holding tank solution added to enough water to cover the bottom of the tank. After adding the solution, use your tank as you normally would.
Use the gray water tank to help clean out the drain hose when emptying the black water tank. Close the water valve the evening before you break camp. In the morning, empty the black water tank first, then the gray water tank. The gray water will clean out the drain hose.
Leave the valves on the gray water tank open when the RV is attached to a sewer system. Gray water tanks don't usually need treatment, but if they begin to stink, use the same chemical solution in the gray water tank that you use in the black water tank.
When it is time to replace a tank, be sure to visit Tank Depot. Tank-Depot.com is the world's largest supplier of marine and RV holding and water tanks.