Minimum dimensions for access fittings and chambers

Internal sizes Cover sizes Type Depth to invert (m) Length x width (mm x mm) Circular (mm) Length x width (mm x mm) Circular (mm) Rodding eye – As drain but minimum 100 – – – Access fitting: small large 0.6 or less 150 x 100 225 x 100 150 – 150 x 100 225 x 100 150 – Inspection chamber 0.6 or less 1.0 or less – 450 x 450 190(1) 450 – 450 x 450 190(1) 450(2) Manhole 1.5 or less over 1.5 1200 x 750 1200 x 750 1050 1200 600 x 600 600 x 600 600 600 Manholes over 2.7 m deep should have a chamber 2 m deep accessed by a shaft 900 x 840 mm or 900 mm in diameter. Notes: (1) Drains up to 50 mm. (2) For clayware or plastic chambers the clear width may be reduced to 430 mm to provide support for cover and frame.