Rain-X

[Bethers]

Yes, I'm serious. Ice is a good cleaner to many things - try it on your coffee pot, also. But, I empty my black tank, close it, take a bag of ice (or two) and put it down the toilet - drive to my next destination (at least a few hours away) and dump it. The motion of the ice in the tank will clean the inside. Of course, doing this more often is better than once a year - but whenever - it will help the tank and is good for it. And can do NO harm. I hate chemicals so when and if I can avoid them, I do.

[rvgrammy1953]

Yep, we do the same with the ice. Works great!!!

[cpatinjones]

Great tip about RainX and ice!