West Siphonics Limited developed the technically advanced "HydroStorm" analytical design software, and the "HydroStorm 75" Siphonic Roof Drainage Outlet and Baffle, tested and approved by Dr Malcolm Wearing and Dr Ray Baker of CRM Rainwater Drainage Consultancy Limited in accordance with the performance requirements of BSEN 12056-3:2000 and BS8490:2007, to cater specifically for the increasingly common flash floods associated with climate change today.

"HydroStorm" software is based upon recognised hydraulic formulae and methodology, including the Bernouli energy equation, to perform the calculations and balance head-losses within the siphonic system. Implementing a siphonic roof drainage system requires the consideration of a number of factors to ensure it will cope with the heaviest of rainstorms as the dynamics of water flow under various conditions are complex and need to be fully understood.

The compact, high capacity "HydroStorm 75" siphonic roof drainage outlets are performance tested and calibrated for flow capacity and water depths and have been developed to make the "HydroStorm" siphonic roof drainage system compatible with virtually any refurbishment or new build. During testing, the "HydroStorm 75" achieved a draining capacity of 41 litres a second, though, in practice, we limit our design to around 20 litres a second to minimise pipe diameters.

The high performance, one piece "HydroStorm" Siphonic Baffle, secured using tamper proof fixings, ensures rapid priming of the system, delivers high flow rates and is designed to resist blockage from gutter debris.