Clause 2.12 (Hydraulic Design – Foul Sewers) 2.12.1 specifies design flows for gravity sewers for residential developments.   System 1 – Foul (Main Drainage Method) enables compliance. 2.12.2 provides design flows for industrial developments, calculated in accordance with BS EN 752-4.   System 1 – Foul (Fixture Unit Method) enables compliance. 2.12.3 self cleansing regime is stated.   System 1 – Foul (Main Drainage Method & Fixture Unit Methods) enable compliance. Foul Design is covered in the Design Fundamentals training course.