Sewers and drains—key definitions
Produced in partnership with John Bates of Old Square Chambers
Sewers and drains—key definitions

The following Environment practice note produced in partnership with John Bates of Old Square Chambers provides comprehensive and up to date legal information covering:

  • Sewers and drains—key definitions
  • Drains
  • Lateral drains
  • Sewers
  • Accessories
  • A drain becoming a sewer
  • Types of sewers
  • Disposal main
  • Effluent
  • Public sewer or lateral drain
  • More...


A ‘drain’ means a drain used for the drainage of one building or of any buildings or yards appurtenant to buildings within the same curtilage.

A drain can also include accessories to it, such as manholes, pumps etc. See accessories definition below.

Whether a structure, such as a row of terraced houses, is ‘one building’ for these purposes is a question of fact.

‘Curtilage’ means in the same boundary or enclosure.

Lateral drains

A ‘lateral drain’ is that part of a drain which runs from the curtilage of a building (or buildings or yards within the same curtilage) to the sewer with which the drain communicates or is to communicate.

Alternatively, (if different and the context so requires) it means the part of a drain identified in a declaration of vesting made under s 102 of the Water Industry Act 1991 or in an agreement made under WIA 1991, s104.


‘Sewer’ includes all sewers and drains (not being drains within the meaning given in drains section above) which are used for the drainage of buildings and yards appurtenant to buildings.

It also includes references to a tunnel or conduit which serves, or is

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