On our over 15000 miles of travel so far this year, we found many Sani-Dumps operated by the State, Municipality or Province, and even some campgrounds, to not have pressured water in the same area as the Sani-Dump.
Many Sani-Dump locations you visit, (especially in the off season
) will not have fresh water to power flush your black tank etc. and this may result in solids being retained at the valve (causing leak
) or in the tank bottom.
Normal procedure is to dump solids first, and then the gray water, as this will help to some extent flush the black tank.
If no pressured water hose is available, try this.
After dumping and draining the black tank, open the gray tank valve, and raise the waste hose above the tank level, thus forcing the gray water into the black tank. Close the gray tank and let the black tank drain again. Repeat this two or three times and you should have almost as clean a tank as you would get with the pressure wash.
It is difficult to clear the black tank valve of the paper products if you don't have adequate water to flush it through.
And of course, always run enough water into the black tank after dumping, to keep the bottom 2" wet.
If you can keep those valves clean, it makes it a lot nicer job the next time you take the cap off.