joefrompa said:Seems to me it would be relatively simply to make a septic system with an alarm/measuring system for the solids and with baffles that last essentially forever. I could be wrong.
I think in most tanks the difference between the "solids" and the "liquids" is very slight, especially at the interface between the two. The solids are in fact mostly liquid, and the liquid, at least the part near the bottom of the 'liquid' layer has a lot of solids in it. There isn't a big difference so I think a sensor would be problematic.