Changes

[[File:Perforations.png|thumb|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.]]  

[[File:Perforations.png|thumb|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]] used in [[bioretention]], [[permeable pavements]], [[infiltration trenches]] and [[exfiltration trenches| exfiltration systems]].  

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.  

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

**Where freezing is a concern, horizontal underdrain pipes should be over-sized to a minimum 200 mm diameter.  

*Perforated pipes should be continuously perforated, smooth interior HDPE or PVC.

**Perforations should be made on all sides of the pipe and provide a ≥ 1 m² of open area per linear meter of pipe.

**Wherever possible pipes should be ≥200 mm internal diameter to reduce potential of freezing and to facilitate push camera inspections and cleaning with jet nozzle equipment.  

**Smooth interior facilitates inspection and maintenance activities; internal corrugations can cause cameras or hydrojetting apparatus to become snagged.   

*At least one vertical well per BMP is recommended, for inspection and monitoring water level.  

**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>.

**Well(s), of 100 - 150 mm diameter perforated pipe, should extend to the bottom of the facility.  

*Non-perforated pipes should be used for conveyance of stormwater to and from the facility, including [[overflow]]. It is good practice to extend the solid pipe approximately 300 mm within the reservoir or practice to reduce the potential for native soil migration into the pipe.

**Where a horizontal underdrain is being installed, an upstream and a downstream well should be coupled to the underdrain pipe. The pair of wells can then be used to flush out the length of underdrain if required.  

 

**The exposed tops of all wells should be fitted with lockable caps.  

*Non-perforated pipes should be used for conveyance to and away from the facility, including overflow.

**To function correctly, the capacity of the overflow pipes must be greater than the inlet(s).

Pipe with connector.jpg|Perforated pipes awaiting installation, note the 45 degree couplings used to facilitate push camera inspection and jet nozzle cleaning.  

[[Category:Materials]]

[[Category:Materials]]