- You can hook up your garden hose (do not use hose used for drinking water or for water utilities) and connect this to the a water connection (usually the onsite water connection). When this is connected and the water is running, this will rinse out the black (sewage) water tank. Be sure to have your sewage hose hooked up to a sewage outlet and have the sewage valve open. When you turn off the water, give the tanks a few minutes to drain before closing the sewage valve and removing the sewage hose.
