I got a new 75 gallon boom sprayer and can"t figure out how to flush out and clean the spray tank. There is a rinse system which appears to clean the boom and the hand held sprayer but not the main tank. There is a screw on cap near the bottom of the tank but it is impossible to reach between the two tanks to open it. Has anyone sprayed with is? /forums/images/graemlins/confused.gif