Anyone replace their tank sensors?

Ours are in an 05 Mh. Always worked. May have to change tommorrow, who knows. It is impractical to try to judge, if the shower is going to overflow by shaking the coach or maybe a long dipstick. We use water Calgon softener, once in a while in black tank and gray tank. Probably not much need. When we empty we follow mfg instructions. The flush system cleans the tank thoroughly including sensors. I has a little container for chlorine tablets but never been able to find them outside the two that came with ll the manuals.