[rohrmann]

It's easier to just forget they exist and just determine when the tank needs to be drained by listening for a burp. The two of us can easily run at least a full week before needing to drain the black tank, and most of the time maybe another 4 or 5 days beyond that. If you just want to spend the money, there are tank sensor systems that have the sensors on the outside of the tank, but you can't use the existing wiring to the panel, but must install the new indicator panel for it to work. We are full time and the sensors haven't worked since the rig was new, and after the first or second fill of the tank, were never reliable. The only sensors that work are from the fresh tank.