As rain falls on the roof, the rainwater spreads out to the lowest level it can find. As the depth of water on the roof or gutter increases, it generates a force to move the water flow towards holes or openings called roof outlets that convey the water to a lower level. The roof outlets are connected to pipes that drop to ground level and into the underground drainage system.

To enable the water to move into the rainwater downpipe from the outlet a large amount of air is required. A vortex forms naturally and the water spirals down the outer wall of the pipe therefore transporting the water flow extremely inefficiently. Current European regulations limit the water/air mix within the pipe to 1/3 water and 2/3 air. This form of water movement results in a large bore pipe moving a lot of air and a little water.

The flow rate is very slow as the water is rotating round and round as it drops instead of flowing directly in the intended course.

The preferred requirements of the architect or building user for free use of the space within buildings is sacrificed due to having limited choice as to the positioning of the numerous rainwater downpipes which are generally determined by the outlets in the roof.

When using the HydroMax™ siphonic roof drainage system, the technology, custom and practice in managing the discharge of rainwater from roofs is changed. A siphonic system maximises the flow of water through the pipes by eliminating air within the pipework and uses the full available building height to drive the water directly through the pipework. Running with full-bore flow by means of simple sphonic action ensures efficient drainage of the rainwater to a connection into the underground drainage system in your preferred location. By using this method you can position the downpipe(s) in location(s) to suit the design teams requirements. The number of downpipes is normally significantly reduced effecting another benefit in respect of a reduction of underground drainage requirements.