Your RV is equipped with storage tanks to hold three types of water. First is fresh water used for drinking, cooking, showers and flushing the toilet. A second type is the waste water you used to shower or wash dishes, commonly called gray water. The third, referred to as black water, is the waste water from the toilet.   Maintenance of your tanks is essential. You should always empty your tanks at a proper dump station. These can found at most campgrounds, some highway rest stops, and at many other locations including truck stops. To keep your black and gray tanks functioning correctly, we recommend emptying the tanks when they are at least 2/3rds full.  The added force of a full tank of water helps to flushaway any solids that might collect in the bottom of your tank reducing holding capacity and fouling tank monitoring sensors. Your fresh water tank should be sanitized regularly following the instructions in your RV’s owner’s manual.