Percolation test procedure for small soakaways

150 mm

The standard percolation test for small surface water soakaways involves boring a 150mm diameter hole, filling it with 300mm of water, and recording the time taken for it to soak away

The standard percolation test for small surface water soakaways involves boring a 150mm diameter hole, filling it with 300mm of water, and recording the time taken for it to soak away. This process is typically repeated and averaged, and then the hole is deepened for a second series of tests to assess permeability changes with depth.

Basis in regulation

BRE Digest 365
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Part H
Approved Document H
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How to check it on site

Confirm that the percolation test steps, including hole diameter, water depth, and repeat measurements, were correctly followed and documented.

Common failure

Inconsistent test methodology, such as varying water fill depths or insufficient repetitions, can lead to inaccurate permeability assessments.

Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.

Related dimensions at this stage

Minimum

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5 °C

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150 mm

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110 mm

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100 mm

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150 mm

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