Stop looking at those level indicators.....LOL
Serious. I haven't looked at mine in over 7 yrs.
They are just a 'stud' that sticks thru this side of tank at different levels.
Scum, crud, deposits, stuff and TP stick to them and thereby make up circuit giving false readings.
They are installed by an evil ex-rv'r to make rv'rs go crazy trying to keep them clean/functioning.
I have a clear adapter that goes on between drain line and drain hose. I can see how well the stuff flows out, when it stops flowing and how clean it is when flushing/rinsing waste tanks.
Besides.....
When toilet 'burps'....time to dump black tank
When sink/shower start draining slower..time to dump grey/galley tanks
When water pump goes....Burrrrrrrup. Should have added water to fresh water tank
That is about 7-10 days for us.