Percolation Testing

August 30, 2019

What is a percolation test?

A percolation test is used to determine the water absorption rate of soil in preparation for building the groundworks of a drainage field. percolation testing is simply examining how quickly a known quantity of water dissipates into the subsoil of a penetrated hole of known surface area.

A percolation test consists of digging one or more holes in the soil of the intended drainage field to a specified measurement. Soaking the holes by directing a high water level in the holes, then running the test by filling the holes to a specific level and timing the drop of the water level as the water percolates into the neighbouring soil. There are various empirical formulae for determining the required size of a drainage field based on the size of the facility, the percolation test results, and other parameters.


A percolation test is mandatory before a drainage field or soakaway can be installed


In order to meet building regulations, a percolation test must be performed three times before the result can be distinguished. The average figure of all three tests will be taken and this will set the type of drainage field or soakaway which is used.

The test must be documented and not carried out in abnormal weather conditions such as heavy rain, frost, snow or drought. The type of ground sitting underneath the soakaway needs to be neither too saturated nor too dry, as both can negatively affect how the wastewater might travel through the soil.

Croft Drainage will complete a percolation test for you, including an in-depth analysis of the ground conditions, design and recommendation for the type of drainage field or soakaway system which is suitable for your ground conditions. Speak to the friendly and local team today, they are available across Lincolnshire, Nottinghamshire and parts of Yorkshire.