Pipes

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Pipes are available with perforations on just one side, these should be situated on the lower half of the pipe. Pipes with 360° perforations should have a strip of geotextile or membrane placed over the pipe to reduce the migration of fines from overlying media.

Perforated pipes are a common component of underdrains, infiltration trenches and exfiltration trenches.

Pipes should have been manufactured in conformity with the latest standards by the Canadian Standards Association (CSA) or ASTM International.

  • Perforated pipes should be continuously perforated, smooth interior HDPE (or equivalent material) with a minimum inside diameter of 100 mm.
    • Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged.
  • Where freezing is a concern, horizontal underdrain pipes should be over-sized to a minimum 200 mm diameter.
  • Perforations should be made on all sides of the pipe and provide a ≥ 1 m2 of open area per linear meter of pipe.
    • A perforated pipe with many rectangular slots has better drainage characteristics than a pipe with similar open area provided by fewer circular holes [1].
  • Non-perforated pipes should be used for conveyance to and away from the facility, including overflow.

See also: flow through perforated pipe


  1. Hazenberg, G., and U. S. Panu (1991), Theoretical analysis of flow rate into perforated drain tubes, Water Resour. Res., 27(7), 1411–1418, doi:10.1029/91WR00779.