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mLine 4:
Line 4: + − *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 m<sup>2</sup> of open area per linear meter of pipe. +
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Pipes should have been manufactured in conformity with the latest standards by the Canadian Standards Association (CSA) or ASTM International.
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.
*Perforated pipes should be continuously perforated, smooth interior HDPE (or equivalent material) with a minimum inside diameter of 100 mm.
**Wherever possible, pipes should be ≥ 200 mm internal diameter.
**Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged.
**Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged.
**A perforated pipe with many rectangular slots has better drainage characteristics than a pipe with similar open area provided by fewer circular holes <ref>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.</ref>.
**A perforated pipe with many rectangular slots has better drainage characteristics than a pipe with similar open area provided by fewer circular holes <ref>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.</ref>.
*Non-perforated pipes should be used for conveyance to and away from the facility, including overflow.
*Non-perforated pipes should be used for conveyance to and away from the facility, including overflow.
<gallery mode="packed" widths=200px heights=200px>
<gallery mode="packed" widths=200px heights=200px>
Perforated Pipe 550x550.jpg|Pipe with slotted perforations
Perforated Pipe 550x550.jpg|Pipe with slotted perforations