Drainage Fields

Drainage Field Installation & Repair

We are experts at installing drainage fields across the south of England. If you have a septic tank then you need a drainage field!

What is a Drainage Field?

A drainage field is similar to a soakaway but is used to disperse the effluent from a septic tank or sewage treatment plant – not rainwater runoff.  It consists of a network of perforated or slotted pipework, running from the septic tank or sewage treatment plant and provides a form of treatment of the waste water, by enabling it to percolate safely through the subsoils and back in to the water table without causing pollution. 

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We offer a professional drainage field installation service across the south of England without the expensive bill.

Understand the regulations

Prior to starting work on a drainage field you will need to check the requirements of Local Building Regulations.

It is illegal to discharge effluent from a septic tank to anywhere but a drainage field. You can receive a significant fine if you were to discharge in to a watercourse as this is in clear breach of environmental laws.

Drainage fields have many regulations such as being a minimum of 10m from a watercourse, 50m from a water abstraction point and 15m from a building. They also need to be sufficiently far away from any other drainage fields, mounds or soakaways. A drainage field cannot be in an Environment Agency Groundwater Source Protection Zone.


Drainage Field installation

Firstly an inspection chamber is created between the septic tank and the drainage field, this allows the drainage field to be accessed easily once it is built.  Trenches are then dug out from the inspection chamber.
The trenches are part filled with gravel before the solid perforated pipes are laid forming a continuous loop.  More gravel is then added on top.  The gravel helps ensure aerobic contact between the liquid effluent and the subsoil.
The trenches are topped with a layer of non-woven geotextile to prevent silt entering the gravel. Finally the topsoil is replaced on top to make the area level.
Older septic tank drainage fields did not have to conform to any Building Regulations and may be a simple long trench, a herringbone drainage layout or even, a large stone filled pit. These latter types are often not fit for the purpose as they are for rainwater only.

Frequently asked questions

How big does a drainage field have to be?

The size and structure of a drainage field is determined by a percolation test and there must be sufficient space available at the property for it to be installed. Furthermore, not all ground conditions are appropriate for a drainage field – if the ground conditions at the property are too wet or too dry, it can prevent the proper functioning of the drainage field. A percolation test will also determine the nature of the ground conditions, and whether or not a drainage field would be appropriate.

What is a percolation test?

Prior to installing a drainage field it is vital that a percolation test is carried out at your property. A percolation test is crucial in assessing the suitability of the ground conditions, and the required size of the drainage field. It is pointless putting a drainage field in clay, as this will simply fill up with water.

What problems can affect a drainage field?

Septic tanks and sewage treatment plants are designed to prevent solid waste from exiting the tank and entering into the drainage field. Damage inside the tank can result in solid waste particles clogging the drainage field, resulting in the drainage system surcharging.

If you suspect that damage may have occurred to your septic tank or sewage treatment plant, it’s important to seek help ASAP.

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Want to know more about soakaways?

Would you like more information about the installation of a soakaway?  Get in touch with our team of drain specialists today to find out more. We look forward to chatting with you and helping you with your soakaway requirements.

Areas Covered

Our specialist drain repair team cover all of Surrey, Hampshire, West Sussex and Berkshire. No matter where you are we will be happy to give you any drainage advice free of charge over the phone.

If you would like to discuss our drain relining and drain repair service with one of our experienced drainage engineers:

Drain lining across the south of England