Roof drainage and guttering

All gutter and outlet systems require routine maintenance regardless of type. Inspections are preferable at least twice a year, more so when gutters are likely to become congested with fallen leaves or other wind blown debris. Detritus should never be swept into gutters and allowed to wash away into the drainage system.

Siphonic systems, because of their reduced pipe sizes and more complex working arrangements are more vulnerable to blockage or malfunction due to lack of maintenance, so it is essential that maintenance staff are fully aware of the way in which the system works and the need to maintain it properly and in accordance with the manufacturer's recommendations.

In conventional gravity systems it is common practice to install leaf guards around outlets to reduce the chance of blockage. Leaf guards can silt up and reduce the flow rates into outlets, in some cases significantly. Under the design codes, the fitting of a leaf guard will mean a 50% reduction in the capacity of the outlet. Leaf guards (or strainers) are usually required for siphonic systems. However, since most siphonic pipes are between 50 and 65mm in diameter they are likely to become congested very quickly with silt, organic matter, construction materials, dead birds and the like (Arthur, S. and Swaffield, J., Siphonic roof drainage, article in Urban Water, Vol. 3, Issue 1–2, 2001, pp. 43–52). If the inlet to the system is restricted, the effectiveness of the siphonic system at large will be compromised. A traditional gravity system may perhaps be slightly more tolerant of silting, but regular maintenance is essential. Equally, safe access for regular maintenance must be provided.