Percolation Testing &
Drainage Field Installation

Percolation Testing

Percolation testing is a service we proudly offer our clients and is a vital step in assessing whether the soil at a site is suitable for installing a drainage field, which is essential for dispersing wastewater from septic tank systems or sewage treatment plants. The test measures how quickly water absorbs into the soil, determining if the ground can handle the consistent flow of treated wastewater without risk of pooling or contamination. If the percolation rate is too slow, the drainage field may not function properly, potentially causing backups or surface overflow. Conversely, if the rate is too fast, wastewater might not be filtered adequately before reaching groundwater. Conducting a percolation test helps ensure the drainage field is designed to work effectively and sustainably, protecting both the environment and public health.

£ 0

In saved costs for clients that did not need to upgrade to a new sewage treatment plant!

Percolation Tests are always conducted over two consecutive mornings/afternoons to allow accurate readings and measurements in calculating a new drainage field design.

A Legal Requirement

When new drainage fields are required, percolation tests are highly important to assess the permeability of the ground and to calculate the size of the new drainage field depending on the test results. They are also a legal requirement in the UK and form part of the British Standards BS 6297:2007.

Drainage fields should not be installed without these must have tests and will not be signed off by building control with out them.

WCDS carry out all drainage field design and installations based on the following factors:

• Test results from percolation tests

• Size of property its serving and number of bedrooms

• Flow rate of the household worked out by the VP (Percolation Value) rating from the percolation test results.

What is a Drainage Field?

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This is the secondary treatment area after a septic tank or a sewage treatment plant for the discharge to pass safely through receiving further treatment from the ground it passes. They are often installed in paddocks/fields or gardens. Drainage fields are a network of pipes that allow the partially treated water to pass via perforated pipes and shingle into the ground.

If you are in a flood zone, a drainage field may not be suitable due to the high groundwater levels typically found in these areas. When groundwater is close to the surface, it can interfere with the drainage field's ability to absorb and filter wastewater effectively.

This excess water can saturate the soil, reducing its capacity to absorb additional wastewater from the system, which can lead to pooling, backups, or even contamination of surface water. Additionally, during heavy rain or flooding events, high groundwater can force untreated or partially treated wastewater to rise to the surface, posing serious health and environmental risks. In these cases, alternative wastewater treatment solutions, such as raised bed systems or mound systems, may be recommended to keep the drainage area above the water table and ensure proper filtration and dispersal.

Drainage Field Maintenance

We often get called out for ineffective drainage field, you may see visual pooling of water or the tank may need emptying more frequently as the discharge is not moving through the ground as it should.

This could mean your drainage field is now exhausted or you may just require a high pressure water jet through of the drainage field to remove any build up or blockages.

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We are always on hand if you need advice, information, or guidance about all the services we offer.
Get in touch with our knowledgeable team today and we can discuss your requirements.

Percolation Testing &
Drainage Field Installation