Standard two compartment septic tank
These septic tanks may be made of plastic, concrete or fiberglass. Each has their advantages. The septic tank provides the primary treatment of the sewage by separating the solids from the liquids in the primary side. They also provide a holding area where anaerobic bacteria can start digesting the solids. As more sewage enters the first compartment, it forces the liquids (effluent) into the second (also called pump or dose) chamber. From the second chamber the effluent is discharge to the soils base treatment area. In Alberta the effluent must be discharged by pump or syphon to prevent the lines from freezing. The primary side of the tank must be capable of hold at least the expected peak volume of sewage produced by the house in one day as well as the accumulated sludge as set forth in the Standard of Practice.
Holding tanks are designed simply to accumulate and hold sewage till it can be transferred to another treatment center. Holding tanks must be watertight. No sewage is allowed to leave the tank except by a licensed seepage hauler. There are some times when installing a holding tank will be the acceptable solution to residential sewage however they should be used as last resort. The cost of pumping and transferring the sewage as well as the impact of the large truck on your driveway and the county roads quickly becomes a liability to the value of your property.