Ensure drainage pipes are sealed to prevent debris from entering the substructure pipe work.

Inspection chamber 320mm diameter have a maximum depth of 600mm.

Check invert level against finished external ground levels to ensure this is not exceeded.

Change to a minimum 450mm diameter chamber if the depth will exceed 600mm.

External drainage must flow in the direction of fall when connecting with the lateral drainage run.

Foul drainage requires an inspection chamber at any change in direction, if this cannot be achieved then within 2m of any change in direction.

Surface water drainage require 100mm of bedding gravel around foul drainage runs including cross overs.

Trenches for external drainage should allow for 150mm of bedding to surround the pipe.

Bedding gravel should be 4mm – 10mm for 110mm pipes.

2mm – 14mm bedding gravel for 150mm pipes.

Additional protection to pipework is required when pipes are laid less than 600mm below finish ground level in garden areas and 900mm below a road surface.

Inspection chambers within driveway should be positioned centrally to avoid tyres of vehicles from driving over the covers.