Approved Document H2 (wastewater treatment)

Approved Document H2 covers the design and installation of small wastewater treatment systems and cesspools where connection to a mains sewer is impractical. While less commonly relevant in Greater London than in rural areas, the document does apply to certain peripheral sites and isolated properties around the M25 fringe. It sets out requirements for septic tank capacity, drainage field design and packaged treatment plants under Building Regulations 2010 and the General Binding Rules for small sewage discharges issued by the Environment Agency. Enforcement is shared between Local Authority Building Control and the Environment Agency, depending on discharge characteristics. Practical implications include the need for percolation testing, separation from watercourses and registered installer certification. The formal reference document is Approved Document H, Volume 2: Wastewater treatment systems and cesspools.