On my first coach the tank level sensor consisted of 4 internal "probes". It wasn't the best system in the world. My solution was simple. I created a "sight glass" for visually seeing the water holding tank level. I Teed off the tank drain, ran clear tubing up to a plugged opening in the top of the tank and had a 100% accurate level depiction with no moving parts or electrical connections.

I do like the Headhunter system we have, but apparently some have had problems with it. Until it pukes I have no plans to change it.