Pumping your system's tanks is vital to the lifespan of your system. A system that is not pumped regularly will eventually fail. The goal of pumping is to remove the solids, fats, oils and greases from your tanks.
Tanks should be pumped when it is 1/3rd full of solids. Pumping should not be confused with a system inspection/evaluation as required by Island County Code 8.07D.
Recommended Pumping Schedule
Washington State Department of Health - Choosing a Septic System Pumper