Siphonic drainage, introduced to Europe in the 1960s, is an engineered rainwater drainage system that utilizes the natural power of a siphon to drain the water from elevated surfaces (roofs, decks, etc).
The system is comprised of a drain, which is designed to inhibit the naturally occurring vortex and an especially configured network of pipe and fittings designed to flow full of water under negative pressure conditions. Pipework can be routed in a building with no pitch or slope, for long horizontal distances, before dropping to low level at a loca-tion to suit the designer, allowing it to be easily coordinated with other services.