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The slot size in surface drains should be kept to a minimum without compromising surface water drainage. There must be a balance between protecting heels, canes, bicycle tyres, wheelchairs and efficient surface water removal

The trade-off between small slots and proper drainage in urban areas

A grate fails hydraulically when water bypass occurs.

Failure to deal with runoff can result in inconveniencing pedestrians to damaging buildings and their contents, disrupt transport systems, interrupt business operations and result in lawsuits associated with injuries to individuals.

A grate’s inlet size has a significant effect on its hydraulic performance and must be considered in real environments particularly when over time grate inlets clog up due to silt and debris. Inlet size however, must be kept to a minimum to stop heels, bicycle and wheelchair wheels;  and walking canes from getting caught.

Special applications

For areas where surface water volumes are low and specific protection is required for stiletto heels, ACO can supply grates, with slot sizes no greater than 8mm that comply with ASME A112.6.3. As small slots restrict surface water collection, ACO offers a free technical service where a grate’s hydraulic intake capacity with blockage factors can be assessed against specific project requirements.

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