black tank flush

You hook a hose up to the attachment outside and make sure that the valves are open on the drain and turn the water on. If you leave the valves shut, think water balloon on the end of a hose. :-) It will wash down the black tank and you should be able to see additional "stuf" coming out of the drain if you have a clear connector. Cant really see the results. unless you have a camera on a cable to lower down the toilet drain to see.