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Porosity and Percolation Tests

"Porosity" or "percolation" tests are carried out to determine how quickly effluent can soak through the sub-soil in the vicinity of a sewage treatment or septic tank installation. This information allows the correct size of soakaway to be designed.

The standard porosity test involves a digging a minimum of 3 different small test holes, which are then filled with water and the time taken for each to empty is noted. We compute the average emptying time which is then used in a British Standard calculation to determine the required size of soakaway.

A porosity test also gives an opportunity of examining what type of sub-soil material is present, e.g. chalk, clay, gravel. Clearly low porousity sub-soils will need a larger soakaway or may not be suitable at all.

Black Water Solutions can undertake porosity tests for domestic and commercial applications.
Small test pit dug to determine topsoild porosity