Siphonic rainwater drainage –

Water Drainage or Siphonic Drainage is a system designed to operate at full capacity where water is sucked or siphoned from the roof into the drain at high velocity. This is achieved by using a special shaped anti-vortex plate at the roof drain inlet which acts as a baffle only allowing water to be drawn off the roof, stopping air being drawn into the pipe. This lack of air coupled with the downwards pull of the water creates a negative pressure which causes the drain pipes to flow at 100% capacity. This high efficiency draining allows fewer and smaller drain pipes to be used. The consequence of the negative pressure means that a traditional push-fit system can’t be used, instead requiring a fully sealed system. Thin wall HDPE pipes, typically SDR 26 or SDR 33 are electrofused with low pressure welds.