Barry
I read a tip on another forum from old timer,, he uses Calgon Water softener in his tank... don't have the numbers of the mix,, it's like 1cup softener to gallon of water,, pours most of it down the black tank and some down the other drains.. claims the mix keeps the sides of the tanks SLIPPERY so nothing will stick to it... we are part time,, so I only put the mixture in when I do a flush first time I flushed lots of gunk, afterwards hardly anything...
sparky