Roof drainage syphon device

A siphon system which utilises a secondary flow to activate the siphon to drain a pool of water 9 comprises three distinct lengths of tubing, the feeding section 2, the drawing section 3 and the siphon section 1, arranged within a vertical plane and connected at a common hub 5. The head 7 of the siphon tube is placed near the lowest point of the pool and the tail of the siphon is connected to the hub. The drawing section extends downwards from the hub and has its lower end open to the air. The feeding section extends upwards from the hub with its upper end connected to a funnel 6. The funnel collects the secondary flow from a suitable source 10 so that it flows down the feeding section, through the hub and into the drawing section, where it accelerates towards the lower end of the drawing section sucking water into the siphon section thus priming the siphon. Once primed the siphon operates independently of the secondary flow. The syphon can be used to drain rainwater from a flat roof.