TGD H 2010 – 1.5.3 – SURFACE WATER DRAINAGE, Siphonic roof drainage systems

1.5.3 Siphonic roof drainage systems Siphonic roof drainage systems should be designed in accordance with I.S. EN 12056- 3: 2000 Gravity drainage systems inside buildings – Part 3: Roof drainage, layout and calculation. Such systems should take account of the surcharge in the downstream drainage system as this can reduce the flow in the downpipe. For long gutters the time taken for the system to prime the siphonic action may be excessive, therefore overflow arrangements should be provided to prevent gutters from over-flowing. For further guidance refer to BS 8490: 2007 Guide to siphonic roof drainage systems

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