A surface water drain collects rainwater run-off from roofs, paved areas, driveways and car parks and conveys it to a soakaway, watercourse, attenuation tank or public surface water sewer. Unlike a foul drain, it does not carry sewage and therefore the discharge is generally cleaner, although it may still contain silt, oils and debris from hard surfaces. In most modern UK developments, surface water and foul flows are kept on separate pipe runs in line with Building Regulations Part H3 and Sewers for Adoption guidance. Many older London properties, however, are still served by combined drains that mix both flows. Where surface water cannot soak away, sustainable drainage systems (SuDS) such as permeable paving, swales or attenuation tanks are often required by local planning authorities.
Surface water drain
Drainage pipe taking rainwater from roofs, driveways and yards to a soakaway or watercourse.
