A typical septic tank has a volume of 750-1500 gallons, and may be made of concrete, steel, or fiberglass. They are watertight chambers that promote the growth of anaerobic bacteria for the biological decomposition of sewage, and the separation of grease and organic particles from the wastewater. Septic tanks are constructed with baffles or sanitary tees to prevent the flow-through of floating solids, and to minimize the possibility of the raw sewage from leaving the tank, and disturbing the settled sludge and floating scum.
A septic system combines a septic tank and a leaching system. The leaching system may include leach lines, leach beds, or seepage pits. Drywells are another term for seepage pits, with the distinction being that they typically handle no sewage and simply re-direct storm water into the ground. Sometimes the term "cesspool" is used, but it's actually archaic. There are a few cesspools manufactured, but they don't permit the flow-through of septic tanks, and are only used for temporary purposes. In terms of modern plumbing, waste from your home enters and exits the top portion of the buried septic tank. In the interim, the bacteria in the tank's liquid environment do their work by breaking down solids into a liquid called effluent. Effluent exits the tank, next enters the leaching system, before finally seeping back into the ground.
When You Need a Plumber
If you begin detecting unwelcome odors, find yourself sinking into soggy and lushly green areas in your lawn, or suddenly discover a fetid backup in your sink, shower, or bathtub, the chances are your septic tank's leaching system has failed. Septic tanks can suffer structural damage or deteriorate over time. Most problems are created by blockages in the plumbing or leaching systems, or the pipe running between your home and the tank. Minor obstructions can be solved with household plumbing equipment, but serious ones require a plumber. Over time, tree roots can also enter the drainpipes choking off the refuse. Also, the soil surrounding the leaching system can become clogged, and when all the sludge and scum is not periodically removed from the tank, they're transported out into the absorption field.
Aside from unclogging pipes, repairing leaching systems, or replacing severely damaged septic tanks, an experienced plumber will know how to find your tank if you don't even know where it is.