How full do you think your black tank really is?

One of the problems is the "Sensors" are kind of hinkey. I mean stick a nail in it (That is basically what the sensor is... a nail).

if it is wet it shows full. (TOp sensor)

I just put a new gravity toilet in my half bath, Once I get the macerator job in the main bath cleaned up I will go back to using only the half bath and park shower and use the main for storage again.

When the tank is full..... NO FLUSH. plus you can see down far enough to know it needs dumping on the last flush.