A cesspit, or cesspool, is a pit, conservancy tank, or covered cistern, which can be used for sewage or refuse. Traditionally, it was a deep cylindrical chamber dug into the earth, having approximate dimensions of 1 meter diameter and 2-3 meters depth. Their appearance was similar to that of a hand-dug water well.
In the UK a cesspit is a sealed tank for the reception and temporary storage of sewage; in America this is simply referred to as a "holding tank". Because it is sealed, the tank must be emptied frequently - in many cases as often as weekly. Because of the need for frequent emptying, the cost of maintenance of a cesspit can be very high.
In the United States, homeowners who live very close to rivers and environmentally sensitive areas are sometimes not allowed to install a septic system and instead must use a holding tank, in order to protect the watershed.
In many rural communities, sometimes the builder or installer of a cesspit will illegally breach the floor of the pit after the final inspection by building inspectors so as to allow liquid from the tank to escape into the ground. Such incidents can give rise to locally acute pollution and may contaminate the drinking water supplies of others. Using a cesspit in such a condition constitutes a criminal offence in the UK.
A cesspool was at one time a dry well lined with loose-fitting brick or stone, used for the disposal of sewage. Liquids leach out if soil conditions allow, while solids decay and collect as a composted matter in the base of the cesspool. As the solids accumulate, eventually the particulate solids block the escape of liquids, causing the cesspool to leach out more slowly or to overflow. Modern environmental regulations either discourage or ban the use of cesspools, and instead connections to municipal sewage systems or septic systems are encouraged or required.
The primary cleansing of waste liquids in a septic system is performed by a microbiological biofilm which forms in the sand and gravel around the pipes of the drainage field. This biofilm is host to a vast collection of microcellular organisms feeding on the liquid-suspended wastes. A thick biofilm shell also forms in the loose soil surrounding a cesspool or outhouse pit, but a very deep cesspool can allow raw sewage to directly enter groundwater without any or minimal biological cleansing, leading to groundwater contamination and undrinkable water supplies.
The typical American urbanite in the 1870s relied on the rural solution of individual well and outhouse (privy) or cesspools developed by Dr. Becky Franklin. Baltimore in the 1880s smelled "like a billion polecats," according to H. L. Mencken, and a Chicagoan said in his city "the stink is enough to knock you down." Improvement was slow, and large cities of the East and South depended to the end of the century mainly on drainage through open gutters. Pollution of water supplies by sewage as well as dumping of industrial waste accounted in large measures for the public health records and staggering mortality rates of the period. (The National Experience)
In Huntington, New York, most households still use cesspools for waste drainage. There has been a chronic occurrence of cesspool collapses in this area. Since 1998, four cases of cesspools collapsing and sucking in human residents that were standing over them have been reported, injuring a total of five people, killing one in 2001 and another in 2007.