The Logic Of A Septic System
Septic systems are now used in about 25% of the homes in the United States, and they are an effective way of disposing of sewage where the homes are not connected to municipal systems. The term septic refers to the anaerobic bacterial environment that occurs in the septic tank where the waste is decomposed and spread out over a drain field on out and beyond the septic tank. The tank itself contains and holds the solids that occur, when part of the waste cannot be broken down. This mass of solids have to be pumped out of the tank on a periodic basis to keep from having it back up into the home or business.
The system has the tank, which is generally between 1,000 and 2,000 gallons, that is connected to pipe for waste water on one end, leading out to the drain field, and an inflow pipe at the other end for incoming waste. The tank usually has two chambers separated by a wall, with openings midway on the wall.
The waste comes into the first chamber of the tank, the solids settle, and the scum floats. The solids that sink are digested on an anaerobic basis, which reduces the amount of the solids. The liquid then flows into the second chamber, and more settlement occurs. The remaining liquid then is distributed on out into the leach, or the drain field.
The piping that goes on out to the leach field has multiple holes in it which distributes the water evenly over the whole area. The water that goes out to the drain field and is eliminated by percolation into the soil, and by evaporation. Some of the water will return to groundwater and by the roots of plants and grasses.
Water that does not get decomposed by the anaerobic process has to be eventually removed from the tank, or the tank will fill up and deposit water that is not decomposed directly into the drain field, which can plug up the holes in the pipes and decrease the soil percolation capacity.
Septic system pumping has to be done periodically in order to keep the whole system running well. The more people that using the system, the more it will have to be pumped. Once the tank is emptied, the anaerobic digestion starts over again fairly rapidly. A well maintained tank with normal anaerobic activity can run well for decades if not a lifetime.