I manufactured a wand to access the gray tank, every 4 years I take the vent cover off and insert the wand with the hose attached, I can only hope that I am getting some of the residue out after pouting water with enough dishwasher detergent and driving around the neighborhood for about a half hour.
I got two 10 foot lengths of white pipe and a threaded coupler for the middle union a shutoff valve and a quick hose connector, there is a cap at the busy end with four holes drilled through at a slight angle so that they spray up, down an in between, there is also one smaller going down and a couple at slight angles.
I remove the cap and insert the assembled wand, the wand is long enough that it touches bottom and still sticks out 3 feet, that way the nephew can rotate the whole contraption and agitate the whole thing while I open the valve, I also have a clear section to watch for clear water, I do not need the wand for the toilet since mine is a straight shot.
navegator