Blackwater Valve Operation
I own a 2009 Sprinter, which I bought secondhand. Tanks were empty upon purchase, or so I was told. I recently drained the black water tank for the first time. When I removed the cap, prior to opening the valve, about one cup of waste spilled out. I caught it and then proceeded to open the black water valve, which did introduce the remainder of the tank contents through the hose.
My question is this: what would cause the valve to "leak" that initial cup of material prior to my release/opening of the valve? And secondarily, how do I avoid this problem in the future?