jeay,

You need to read up on septic systems so you have a general understanding
of how they work. Maybe your ag exten guy has a leaflet. Your public library
will have books on this. Putting large quantities of grease into a septic
system is a no no. Are you sure that the septic system is sized
appropriately for the number of residents? The comment about hair makes me
think you are showering an entire college dorm into a single family septic
system. Needing 3 pump outs in a year is very odd.
$650 seems a bit much for 2 pump outs to me, what do your neighbors pay?

Dave M.