Last edited 29 Mar 2021


According to BRE Digest 365 Soakaway design: ‘Soakaways are used to store the immediate surface water run-off from hard surfaced areas, such as roofs or car parks, and allow for efficient infiltration into the adjacent soil. They discharge their stored water sufficiently quickly to provide the necessary capacity to receive run-off from a subsequent storm.’

Traditionally they have been used as a way of disposing of surface water in areas that are remote from public sewers or watercourses, instead allowing rainwater to infiltrate directly into the ground. However, recently they have also been used in fully-sewered areas to limit the impact of new building works and to avoid the cost of upgrading sewers.

They can be square, circular, or trench excavations and can be filled with rubble, or lined with brickwork, plastic cells, perforated pre-cast concrete ring units or similar structures. They can also be deep bored.

NB The SuDS Manual (C753) published by CIRIA in 2015, defines a soakaway as: ‘A subsurface structure into which surface water is conveyed, designed to promote infiltration.’

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