What This Requirement Covers
Inspection chambers and manholes provide access to below-ground drainage systems for maintenance, cleaning, and repair. Approved Document H requires access points at key locations in the drainage system to enable rodding, jetting, and inspection.
Key Requirements
Where Access Is Required
- At the head of each drain run
- At changes of direction (greater than 45 degrees)
- At changes of gradient
- At changes of pipe size
- At junctions (where drains connect)
- At intervals not exceeding 22 metres for 100 mm drains or 45 metres for 150 mm drains
Types of Access
- Rodding eye: A capped access point at the head of a drain run; allows rodding in one direction only
- Inspection chamber: A chamber deep enough to allow access for inspection and rodding; maximum depth 1.0 metre (for plastic chambers) or 1.2 metres (for concrete)
- Manhole: A chamber deep enough for a person to enter; required where the invert depth exceeds 1.0 metre
- Access junction: A junction with an access cap for rodding; limited to shallow drain runs
Construction
- Plastic inspection chambers (e.g., Wavin, Polypipe) are the standard for domestic installations up to 1.0 metre depth
- Concrete or brick manholes are used for depths exceeding 1.0 metre or where heavy traffic loads apply
- Covers and frames must be appropriate for the load (Class A for pedestrian areas, Class B for light vehicles, Class D for heavy vehicles)
- Covers in buildings must be double-sealed and screw-down to prevent foul air entering the building
Practical Compliance Tips
- Plan inspection chamber locations at the design stage to ensure they are accessible for maintenance
- Do not place inspection chambers under permanent structures or paving that cannot be lifted
- Use screw-down double-sealed covers for any inspection chambers within or adjacent to buildings
- Ensure the channel and benching in the base of the chamber guide flow through without obstructing rodding access
- Test all chambers for watertightness along with the rest of the drainage system
- Provide accurate records of inspection chamber locations and depths for the as-built drawings
- Consider future access needs; inspection chambers should be accessible by drainage contractors with rodding and jetting equipment