A good sewer hose is well worth the money, and throw away the cheaply that probably came with your RV. Clear sections are a necessity. My Greyhawk has a rinse connection for the black tank. After draining the black, followed by the gray, I turn on the rinse hose, close the drain valves and, let the black tank fill 50% or more (be careful not to over fill), then dump it again! and if it's not perfectly clear I do it again.