[Andy N1ORK]

For my park model in Freedom, NH, I installed a black tank 'spinner' that hooks up to a waterhose. I turn on the water and it spins water around the tank helping to clean it. I do this a few times until the see through coupling runs clean. I shut off the water, drain the tanks then close both the grey and black tank valves. Then I pump RV anti-freeze through the system. The excess goes into the tanks. This procedure works well for me.