[jfaberna]

I agree with Rondo. You will never completely clean your black tank. You want to keep it functional. There are a number of organic, enzyme based treatments. Some are powder and some are liquid. I find most of them work as advertised in black and grey tanks to control odor and breakdown waste.

None will fix your sensors. Mine quit working in all 3 waste tanks after the first camping trip 6 years ago.

I find that if you are on your last leg of your trip home, I setup all 3 tanks with 3 gallons of water and treatment. It will slosh around and treat the tank best it can. Then I drain at home. In my case I use a macerater and pump it to a sewer clean out.