Manhole
/ ˈmanhəʊl /
Also known as: access chamber, drain chamber, sewer chamber, inspection chamber
Definition
A manhole is a below-ground access chamber at junctions, changes of direction, and maintenance access points in a drainage or sewer system. A true manhole is deep enough to enter (typically over 1m), with step irons and minimum internal dimensions of 1050 x 800mm. Shallower access points are inspection chambers. Inside, the channel carries flow along the base and benching (sloped concrete either side) rises to the walls. Covered at surface level by a load-rated cast iron or ductile iron cover and frame (A15 for pedestrian/garden; B125 for driveways; D400 for roads). Governed by Building Regulations Approved Document H.
In practice
Manholes on private drainage (within the property boundary) are the owner's responsibility to maintain. Manholes on adopted public sewers (transferred to the water company) are the water company's responsibility from the point of adoption - though this only applies to sewers adopted under the Water Industry Act, not to private shared drains. Shared private drains (serving more than one property but not adopted) remain the shared responsibility of all connected properties under the Defective Premises Act, which can cause disputes when maintenance is needed.
Manhole covers in driveways are frequently replaced with recessed tray covers - a frame with a recessed tray that can be filled with block paving, tarmac, or other surface material to match the driveway. This is acceptable but the recessed cover must be rated for vehicular load (B125 minimum for private driveways) and the access must remain operable - filling the recess with permanently bonded material that prevents opening the cover is not acceptable as it prevents access to the drain for maintenance.
Building Regulations
Approved Document H (Drainage and Waste Disposal) requires drainage access at all junctions, changes of direction greater than 45 degrees, and at intervals not exceeding 45m on straight runs. The access may be a rodding eye, inspection chamber, or manhole depending on depth and maintenance requirements. Covers and frames must be to BS EN 124 and rated appropriately for the traffic loading. Entering a manhole is a confined space entry - under the Confined Spaces Regulations 1997, this requires a risk assessment, permit to work, gas monitoring, and trained rescue provision. Even in domestic drain maintenance, operatives should not enter manholes alone.
Full Building Regulations guidanceSee also