Septic tanks and cesspools are two methods of disposing of liquid household waste in rural areas that do not have access to public sewer systems. Septic tanks are generally considered to be an improvement over cesspools.
A cesspool is usually a simple pit that is dug in the ground and lined with concrete blocks or rocks. Septic tanks are closed containers, usually made of concrete, that are installed underground. Septic tanks are usually only one part of a septic system, which is usually also comprised of a drain field.
Both cesspools and septic tanks receive waste water from houses via pipe. Whereas cesspools simply store waste water, septic tanks and septic systems treat waste water so that it may be safely returned to the environment.
The advantage of cesspools lies in the fact that they are relatively simple and inexpensive to install. Septic tanks are more complex and expensive, because they often require large underground drain fields to fully treat waste water.
Generally, septic tanks and systems perform as expected, and make waste water safe to return to the environment by removing pollutants as well as dangerous viruses and bacteria. Cesspools, on the other hand, often contaminate nearby wells and groundwater supplies as hazardous household waste slowly seeps out of them.
Septic tanks and systems are an accepted form of waste water treatment in rural areas. Cesspools, on the other hand, are considered to be dangerous to the environment and to drinking water supplies, and have been outlawed in many states.