If you lived in this progressive state you wouldn't have to ask that question. It is a law that it has to be pumped every three years.
Had to put in a new system two years ago. The old tank (750 gal.) was left in and a new one !,000 added. I live by myself but I still must have the system pumped every three years.
Now if I can produce 1700 gallons of solid nonbiodegradable solids in three years,I have a bigger problem than the $150+- it costs to have it pumped according to law.