The hydraulic principles governing the performance of conventional and siphonic roof-drainage systems are considered in this Techtalk.
The flow rate in a conventional system is determined by the depth of water in the gutter or on the roof. Siphonic systems are able to achieve higher flow rates because they make full use of the head available between the roof and the discharge point at ground level. Some special operating characteristics of siphonic systems are described and recommendations are made on the factors that should be considered in their design by Geberit based on their corporate experience gained from over 40 years knowledge in siphonic roof drainage..
Geberit outline an essentially 6 step process to Designing a syphonic drainage system
- Calculation of the roof area.
- Determining the rainfall intensity.
- Volumetric flow of the roof area.
- Number a position of the roof outlets.
- Defining the pipe routing in CAD mainly
- Design software schematic.
For greater details see SIPHONIC RAINWATER SYSTEMS presentation here .