Drainage fields: questions worth asking

Start with the outlet

England’s regulator distinguishes sewage discharged to the ground from sewage discharged to surface water. The required checks depend on that route and when the discharge started or changed.

• Ask for a plan showing the tank, pipework, field or outlet and land ownership.
• Do not assume that the word “soakaway” in an advert establishes a suitable sewage drainage field. Ask the installer to specify its proposed system.

A direct watercourse discharge in England

If an English septic tank discharges directly to a watercourse, the EA says action is needed as soon as possible. Its options include a sewer connection, a treatment plant or a suitable drainage field meeting the ground-discharge rules. Ask the regulator or competent installer which route is appropriate.

Ask about investigation and design

• What site investigation or percolation information is needed?
• Where will the proposed field be, and what land or access rights are needed?
• How does the design account for the discharge volume and site constraints?
• Which regulator conditions and other permissions apply? Ask for written answers rather than treating this guide as a design approval.

Keep repair and replacement proposals comparable

• Ask what evidence supports the proposed work.
• Request a plan, scope, disposal arrangements, reinstatement details and exclusions.
• Do not select a design on price alone without understanding what has been assessed.