I wish to show the fill level of septic system pump tank

You could look at the Haas implementation of a Zigbee device [see this thread]
(Thingshield replacement for arduino over zigbee now available for hubitat) I have a few working and they are trouble free.
The device has analog inputs the will directly interface with Hubitat. @ogiewon wrote a Hubitat driver so it can almost be plug and play.