RE: Tank Level monitors
*** They are fine (actually great!) for water & fuel tanks but terrible for waste.
Except for a plastic tank and a flashlight , or feeling a flex tank, everything stinks at measuring a waste vtank.
Insteas of cleaning or replacing senders the simple use of a puff of air will clear the system , for a while.
If it mus be maintained , at least this is done remotely and cleanly.