Last edited 05 Jan 2018


Sewerage (the sewer system), is the underground networks of pipes that carries sewage (waste water and excrement), waste water and surface water run-off, from buildings to treatment facilities or disposal points.

Types of sewer include:

  • Sanitary sewer: Used solely for carrying sewage.
  • Surface water sewer: Used to drain groundwater and excess water from impervious surfaces.
  • Combined sewer: Used to carry both waste and storm water. This type of sewer can lead to water pollution problems when overflow conditions are experienced.
  • Effluent sewer (sometimes referred to as Septic Tank Effluent Drainage (STED) or Solids-Free Sewers (SFS)) : These collect remaining sewage from septic tanks and carry it to a treatment plant.

There are a number of ways of moving the contents of sewers:

  • Gravity sewers use differing elevations to facilitate movement.
  • Force mains use pumps where sewers are at a lower elevation than the destination.
  • Vacuum sewers use differential atmospheric pressure.

On 6 September 2010 the government announced that most private sewers that connected to the public sewer network would be transferred to the ownership of the regulated sewerage companies in England and Wales. Private sewers that were connected to the public sewer network before 1 July 2011 were transferred on 1 October 2011.

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