New to me; I've never heard of the black tank flushing system being inside the "house" part of the trailer. Our Grand Junction's system only had a hose connection outside with the PEX tubing running directly to the black tank, the backflow preventer was just prior to the black tank, under the floor. There is no water pressure regulator in the flushing system, it would defeat the purpose, because it is never closed, the spray-head is always open. At home my outside hydrants are unregulated,and line pressure is 100psi. It rinses the black tank very well, and the sound of the swirling spray is obvious.
As to low CG water pressure, I have experienced the same lack of spraying sound often.
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"