Pipes

• Perforated pipes should be continuously perforated, smooth interior HDPE (or equivalent material) with a minimum inside diameter of 100 mm. Where freezing is a concern, horizontal underdrain pipes should be over-sized to a minimum 200 mm diameter.
• Perforations should be 10 mm in diameter and distributed at least every 90 deg around the pipe.
• All underdrains should be capped on the upstream end.
• At least one vertical well per BMP is recommended, for inspection and monitoring water level. Well(s), of 100 - 150 mm diameter perforated pipe, should extend to the bottom of the facility. 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, overflow pipes must be larger in diameter than inlet pipes.

A perforated pipe used to assist the draining of soils.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.