Black Tank Sensor Lies

My black tank says full. It's not full. I just emptied it. The sensors lie. They lie to everyone.

RV black tank sensors are three to four prongs mounted inside the tank wall. They read fluid level by electrical conductivity between prongs. When toilet paper bridges across the prongs — they read 'full' forever after.

Submission this week from a viewer who paid eight hundred dollars to a dealer to 'fix' the sensors. Dealer cleaned them, sensors lied again two weeks later. The fix isn't a fix. The design is the problem.

Solution one — ignore the sensors. Track tank usage by time. Family of four, average tank capacity, dump every four to five days regardless of reading.

Solution two — aftermarket external sensors. SeeLevel II is the most common. Attaches to the outside of the tank wall, reads through. Doesn't have the prong-fouling problem. Two-fifty for a kit. Worth it.