Should rainwater or surface water enter my foul drainage system?

No. Rainwater and surface water should never enter a septic tank or sewage treatment plant. These systems are designed to treat sewage only, and are sized accordingly. Rainwater entering the system will overwhelm the treatment process, carry settled solids and bacteria into the drainage field or watercourse, and block or destroy the drainage field over time. Building Regulations (Part H) require rainwater and surface water drainage to be kept completely separate from foul drainage. If you suspect rainwater is entering your system, contact us – identifying and eliminating this is one of the most common and important maintenance interventions we carry out.