Drainage Fields, Percolation Tests & Soakaways

Independent Drainage – your local specialist for wastewater management and percolation tests.
Specialists in waste water management & percolation testing.
We help homeowners, landlords and businesses with wastewater management from septic tanks and sewage treatment plants. Our drainage experts carry out percolation tests, drainage field installation and soakaway installation. 


Our expert team carries out drainage field installation, to disperse and treat the outflow from either a septic tank or sewage treatment plant. We’ll undertake a percolation test before installation, to make sure the ground is suitable and to calculate the volume of the drainage field.


A drainage field installation consists of rigid, perforated pipework, buried underground. The perforated pipes are laid in a clean stone surround with a membrane layer, before being covered with soil.


The final outflow from a sewage treatment plant or septic tank travels through the entire length of the drainage field – passing through the perforations and into the clean stone surround. Here, anaerobic bacteria break down waste further, before the water is absorbed into the surrounding soil.


The volume of the drainage field is calculated in linear metres and sized depending on the soil type and number of residences the property can accommodate.

In a Ground Water Protection Zone, a septic tank and drainage field is not permitted – however, with a permit from the Environment Agency, a sewage treatment plant and drainage field may be permissible, subject to the Environment Agency’s General Binding Rules.

Drainage Fields
Percolation Test


Before a drainage field installation, the Environment Agency and Building Control require that percolation tests are carried out in all types of soil.

A percolation test reveals the suitability of the site for a drainage field, helps make an accurate drainage field size calculation and protects the environment. Percolation tests check that the drainage field will allow wastewater to soak into the soil without saturating the ground.

The percolation test itself is done by digging three holes at the site of a proposed drainage field, and then filling the holes with a specified amount of water. The absorption is timed, in seconds per mm. The result of the percolation test will let us know if the ground is suitable for a drainage field installation, and allows us to calculate the required volume for the drainage field. A percolation test also ensures that the water table will not be contaminated with pollutants. 

Independent Drainage has extensive experience in conducting percolation tests for the installation of drainage fields. Get in touch with us today for a free consultation.




A soakaway is designed to take rain and surface water, to avoid pooling and flooding. A typical soakaway installation is of a pit-style construction, with concrete rings or plastic crates, which acts as a void for water to collect in and disperse safely into the surrounding soil.


A soakaway would not usually be considered for use with a foul water discharge. 


However, if a property is too small for a drainage field installation, a soakaway can be considered as a viable alternative. Septic tanks can’t be discharged into a soakaway due to the rudimentary wastewater treatment they provide. A soakaway installation will only work with a sewage treatment plant – and a permit will be required from the Environment Agency to do so.


Need advice on a soakaway installation? Talk to our friendly team of experts today.

South of England Map
Need more information? 

We are here to assist. Contact us by phone, email or via our social media channels.

Thanks! Message sent.