What is an inspection chamber?

An inspection chamber (IC) is an underground access point in a drainage system that allows drains to be inspected, tested, rodded, and cleared of blockages without excavation. It consists of a chamber base (usually precast concrete or polypropylene) containing half-channel benching to direct flow, a riser section, and a cover and frame at ground level. Inspection chambers are required at every change of direction, change of gradient, junction, and at intervals along straight runs of drain.

What is the difference between an inspection chamber and a manhole?

Both provide access to drainage systems, but they differ in size. An inspection chamber is typically 450-600mm internal diameter and is too small to enter - access is by rodding arm or camera. A manhole is large enough for a person to enter (minimum 1200mm x 675mm in plan) and is used for deeper drains or complex junctions. For domestic drainage, inspection chambers are far more common. Approved Document H uses both terms - 'inspection chamber' for shallower access points and 'manhole' for deeper ones.

Where are inspection chambers required?

Approved Document H requires inspection chambers at: every change of direction greater than 45 degrees; every change of gradient; every junction of two or more drains; the head of every drain run; and at maximum spacings along straight runs (22.5m for 100mm pipes when rodded from both ends). They must also be positioned so that each drain run between chambers can be accessed and cleared without removing more than one cover.

What cover is needed on an inspection chamber?

Inspection chamber covers are classified by their load-bearing capacity. In pedestrian-only areas (gardens, footpaths), Class A (5 tonne) covers are used. In driveways and car parking areas, Class B (12.5 tonne) covers are required. In road applications, Class D (40 tonne) covers are needed. The cover must sit flush with the surrounding surface and must be lockable or double-seal in areas where odour or insect ingress is a concern.

Drainage & Utilities noun

Inspection Chamber

/ ɪnˈspɛkʃ(ə)n ˈtʃeɪmbə /

Also known as: manhole, access chamber, IC, drainage access point

Definition

An inspection chamber is an underground access point in a drainage system that allows pipes to be inspected, tested, rodded, and cleared without excavation. It consists of a chamber base containing half-channel benching that directs flow, a riser section to ground level, and a cover and frame. Building Regulations require inspection chambers at changes of direction, gradient, junctions, and at regular intervals along drain runs.

In practice

Modern domestic inspection chambers use polypropylene (plastic) base units with pre-formed channel benching and a range of inlet and outlet connections. They are available in 315mm, 450mm, and 600mm internal diameters with risers in 150mm height increments. The base unit is bedded on 150mm concrete, the riser sections bonded with solvent cement, and a pressed steel or ductile iron cover and frame set at finished level.

Concrete precast inspection chambers are used for deeper or more heavily loaded situations. Every inspection chamber must have a minimum 150mm diameter inlet and outlet - 100mm domestic drains increase to 150mm at the first inspection chamber to improve self-cleansing velocity. The cover type must match the load rating of the location: Class A for pedestrian, Class B for vehicles. In driveways, covers must be set in a concrete surround and bedded on mortar to prevent rocking.

Building Regulations

Relevant PartPart H - Drainage and waste disposal

Required atEvery change of direction, gradient, and junction

Max spacing (100mm pipe)22 m rodded from one end, 45 m from both ends

Cover loadingClass A (5t) pedestrian, Class B (12.5t) vehicles

Approved Document H Table 5 sets out maximum distances between access points for different drain sizes and whether rodding access is from one or both ends. Inspection chambers must not be located under building foundations or in positions where they would be inaccessible. Where a drain passes under a building, an access point must be provided at each end of the section passing beneath the structure.

Full Building Regulations guidance

Inspection Chamber

Just so you know...