Ok, lots of different remedies here. Some good, some bad. So, I'll add my 2 cents.
I've owned several different types of rv's from pop-ups to our current mh. What I've always done to keep my tanks clean and in perfect operational condition (including my sensors) is this:
When getting ready to travel, I'll dump both tanks and rinse the black with the in-tank rinsing device. If you don't have one, I suggest you have one installed (fairly easy job). Then I'll dump again and add about 5 gallons of fresh water along with a cup full of liquid laundry detergent (I use Oxy-Clean) in both tanks. I'll then drive to my next destination and once there dump the soapy solution from the tanks and add several gallons of fresh water and use the tanks normally. The next time I travel, I repeat this process. If you can get your hands on some liquid Calgon water softener, add a cap full, or two, along with the cup of detergent. The Calgon will make the inside of the tanks slippery...hindering anything sticking to it (or the probes).
Keep in mind that water, lots of water, is your friend. When either using the toilet or dumping the tanks, use lots of water. ALWAYS keep water in both tanks....never let them dry out.
Again, this is my proven solution that has worked for me for years and years. It will even keep the odors down so that no black tank chemicals is required...ever.
Like I said... my 2 cents. Take it or leave it.
Ron
