You have a sewer hookup, so if you can fill the black tank with water and RidX, Roebic K40 lateral line cleaner, or other such product; allow it to sit for a week or as long as possible before dumping the contents into your sewer hookup. You don't need the force of pressurized water to clean the tank. If it is full ,the force of the evacuating water will carry out any solids remaining after one of those additives does its job.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"