Originally Posted by Roadfrog
Yes, there should be at least 4 on each tank. Simply unscrew it as much as you can and just pop off the sensor. The rubber grommet that the screw goes into has a small nut in it that is the sensor. Pop out the grommet with pliers or whatever and pop the new sensor/grommet in. When you tighten the screw, it swells the grommet to form a seal on the tank. Trust me, this is a simple job if you can get access to the sensors. Some tanks are hard to get at. Mine was not and it sounds like yours aren't either. You could even just clean teh sensor when you take it out and reinstall it if you prefer.
I installed flushers that install in the tank that I got from camperworld that do a great job of flushing the tanks--- called no fuss flushers these clean the tanks realy good. just thought I'd pass that along.