A manhole or maintenance hole is the top opening to an underground vault used to house an access point for making connections or performing maintenance on underground and buried public utility and other services including sewers, telephone, electricity, storm drains and gas. It is protected by a manhole cover, a (usually metal) plug designed to prevent accidental or unauthorised access to the manhole.
Manholes are generally found in urban areas, in streets and occasionally under sidewalks.
In rural and undeveloped areas, services such as telephone and electric are carried on pylons.
Maintenanceholes: are covered openings placed in the pipe line to permit access approximately every 150 metres for inspection, cleaning and maintenance.
Air valves are often mounted on the access maintenancehole cover in a chamber.
They are always incorporated on a standard access maintenancehole cover to allow entry at the drain point.
Maintenanceholes should be of a size and shape that provides reasonable access for personnel and equipment to flow channels, with a minimal likelihood of problems.
Maintenanceholes are to be constructed where sewers, or property ties of DN150 or larger, form a junction with a main sewer.
Maintenanceholes may require bolt-down locking to resist internal surcharges, in this case stainless steel bolts are to be used to secure the cover to the seating ring.
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