Septic Systems 101
Our Cornell Cooperative Extension, as part of an education project supported by a grant from the Water Resources Institute at Cornell University with funds provided by the NY State Legislature through the NY State Dept of Agriculture & Markets.
Your septic system has two basic working parts:
1) Septic Tank - wastewater flows from the house into the septic tank. Here heavy solids settle and are partially decomposed by bacteria to form sludge. Light solids and grease float to the top forming a scum layer.
2) Soil Absorption Field - partially treated wastewater is discharged from the septic tank through perforated pipes into an absorption field. Here, the water is further purified by filtration and decomposition by microorganisms in the soil.
It is recommended septic tanks should be pumped every 3-5 years, depending on the size and amount/ quality of solids entering the tank. For example, Cornell Coop Ext. advised 1000 gallon tank used by a family of two should be cleaned after 5 years; and if a garbage disposal is in usage, it increases the load about 50%. Maintaining your septic system is described in the Cornell's fact sheet (click here pg. 1, pg. 2).
Contact the Cornell Cooperative Extension for their Publication PS-1. A handy easy to understand file of septic facts and charts.