While there has been a steady decline, as many as 40% of all households in some areas still rely on some sort of private onsite waste disposal or sewage system. A cesspool is one of the earliest and most basic types of wastewater treatment systems.  A cesspool is, simply put, a hole in the ground.  In earlier versions, the hole was lined with stone or block; most modern ones are lined with concrete.  In either case, wastewater travels from the plumbing fixtures to the house drain line directly to the cesspool. Solids settle to the bottom and the liquid seeps through gaps in the loose laid stone or block, or holes in the concrete, into the surrounding soil.  A cesspool works best when installed in sandy soil.

Normally, the solid matter that accumulates in a cesspool has to be removed at least annually, but in some cases much more frequently.  Overtime, the absorption rate of the soil tends to decline requiring abandonment and relocation of a new system. 

In most areas, cesspools are no longer an acceptable means of providing onsite wastewater treatment.  Instead, either a conventional septic system or an alternative type onsite wastewater system must be used.  The major elements of a septic system are a tank and drain (absorption) field. The tank is generally a precast concrete chamber. Its purpose is to provide a holding area for the liquid and solid waste as an organic bacterial breakdown of the solid waste occurs.

As more waste and water enters the tank, the solids settle to the bottom to be broken down while the liquid waste and broken down solids (effluent) flow out into the absorption field system.

A conventional septic system’s drain field consists of perforated plastic piping set in a bed of gravel, or a seepage pit, which is actually similar to a cesspool. If properly designed for the size of the house and type of water-using fixtures or appliances present, a septic system can function for several years, sometimes even longer, before solids have to be pumped out. In addition, the wastewater that seeps into the soil is “cleaner” than that flowing directly from a cesspool.  Alternatives to conventional septics, typically designed to address problematic soils or site conditions, include the use of drainage chambers, sand filters, and aeration systems.