This is essential for making sure your black tank is truly clean when dumping. Our coach has a black tank rinse where we can connect a hose to put water into the black tank while dumping. We open the black valve and observe the water to see if there are any more solids in it. The only way to see the water is to have a clear adapter either at the sewer connection or the valve end. This is a must for keeping tanks clean and smell free.