Your waste system is made up of your toilet, sinks, shower, a gray tank, and a black tank. Your gray tank is for the water waste that comes from your sinks and your shower. The black tank is specific to your toilet. Usually these tanks are often about 40% of what the freshwater system can hold. Thus a 100 gallon fresh water tank will often have a 40 gallon gray tank and a 40 gallon black tank. Some RV’s may have more than one of either of these tanks (multiple bathrooms, for example). EACH tank has its own flush handle – one for gray, one for black, and one for any third tank you might have.
Your sewage system will also contain a “black tank flush”. This allows you to put water into the black tank in an effort to help flush the solids from the tank. There are a few tips and tricks to know about dumping and flushing your tanks. This information, and much more, is available in the RV Masters “How To” series.