Siphonic Drainage System

Pipework in siphonic drainage system are;

• Smaller in pipe size,
• Lesser number of rainwater downpipes,
• Higher flow velocities,
• Superior when comes to drainage capacity,
• Generally with zero gradient on horizontal pipe run,
• Ease in site coordination to installation due to its flexibility,
• Minimal roof outlets with high drainage capacity,
• Self-cleansing effect due to high flow velocity within the pipework.

Siphonic systems are engineered on the concept of full-bore flow (fill rate of 100%) of uncompressible fluid.

System for drainage of rainwater in which the outlets and pipework enable the system to flow completely full under design conditions and make use of the total height available between the outlets and the point of change to partially filled flow.

A closed-flow roof drainage system operating under gravity-induced sub-atmospheric pressures based on the vertical differential fluid head principle (the height of a column of water expressed in pounds per square inch pressure or equivalent metric units).

Siphonic rainwater drainage system pipework has gone through engineering calculation.

The design of siphonic system should be determined by calculating the total head losses in the pipes and fittings at the design flow rate and ensuring that the recommendations given for minimum pressure, minimum velocity, degree of balancing between outlets, and speed of priming are met. Values of pressure and velocity in the pipes should be calculated at all changes of direction or diameter in a system in order to ensure that the lowest values of these parameters are identified and are within the allowable limits.

References

1. BS EN 1253-1:2003
2. ASPE ANSI-45:2013
3. BS EN 8940:2007