thumb|[[Postmaster-General's Department|PMG manholes in a city street, Perth, Western Australia]]

thumb|[[Sanitary manhole|Manhole being used to access sewer]]

thumb|Installation of a fiber-optic manhole in [[Brooklyn|Brooklyn, New York]]

thumb|An uncovered manhole in [[Beirut, Lebanon]]

A manhole, also called utility hole, maintenance hole, or sewer hole, is an opening to a confined space such as a shaft, utility vault, or large vessel. Manholes, typically protected by a manhole cover, are often used as an access point for an underground public utility, allowing inspection, maintenance, and system upgrades. The majority of underground services have manholes, including water, sewers, telephone, electricity, storm drains, district heating, and gas.

Manholes are generally found in urban areas, in streets and occasionally under sidewalks. In rural and undeveloped areas, services such as telephone and electricity are usually carried on utility poles or even pylons rather than underground.

In Australia, manhole also commonly refers to an access hatch used to get access from a room or hallway into the ceiling cavity of a building. These manholes are typically around square.

Construction

thumb|[[Manhole covers in Helsinki, Finland]]

Manhole closings are protected by a grating or manhole cover, a flat plug designed to prevent accidental or unauthorized access to the manhole. These covers are traditionally made of metal,

Manholes are usually round, primarily because roundness is the best shape to resist the compression of the earth; covers are round because they are easier to move by rolling, and they can't fall into the opening. But in the United Kingdom they are nearly always square, or rectangular, in shape, at least at street level. Manholes can also be found in a triangular shape (e.g. in Cambridge, and surrounding villages).

Composite manholes

Composite (fiberglass) manholes are commonly used in applications where infiltration, exfiltration, or corrosion by hydrogen sulfide (from sewer gas) are a concern, or where structures need to be factory integrated into a manhole before placement. In these manholes, the entire underground enclosure is constructed of some composite material, in addition to the cover.

Structures that can be integrated into composite manholes include:

  • Flow inverts
  • Flumes
  • Drop structures from higher elevation flows to lower elevation discharge pipes
  • Weirs
  • Storm water screening structures
  • Sewage grinders
  • Energy absorbing structures to dissipate undesirable flow stream turbulence or velocity

Hazards caused by manholes

In urban areas, damaged or uncovered manholes and stray voltage issues have become a significant concern.

On January 16, 2004, Jodie S. Lane was electrocuted after stepping on a metal manhole cover, while walking her two dogs in New York City.

Failures of underground electrical lines can cause fires and sudden releases of energy that blow manhole covers into the air and may injure pedestrians or cause property damage. Some utilities have installed safer covers that can vent hot gas while remaining attached to the ground, using metal rails.

Sewer manhole location

thumb|Truck with manhole cutter in [[Dnipro, Ukraine]]

The location of a sewer manhole must be carefully considered to ensure that the drainage system is effective and easy to maintain. According to design standards, the distance between two manholes is typically between 7 and 20 meters, depending on the specific characteristics of the project. In cities, the distance is 20 meters per manhole, while in industrial or commercial settings it is 10-15 meters per manhole. The distance between manholes in homes or restaurants is typically 7-10 meters.

<gallery class="center">

File:Open Manhole and Cover Mid-City New Orleans.jpg|A round manhole in New Orleans, and its cover

File:Bueirocemig.JPG|Manhole cover in Belo Horizonte, Brazil

File:Cambridgeshire Manhole.jpg|Manhole cover in Sawston, Cambridgeshire

File:Manhole.jpg|Installation of a sewer manhole. Upon completion, typically only the top ring and cover (not pictured) would be visible.

File:- Manhole cover in Germany -.jpg|Manhole cover of precast concrete in Germany

File:Manhole without manhole cover in Villebon-sur-Yvette 4.jpg|Storm drain manhole without cover in France

File:ManHoleDoorFoundersHallGirard1840.jpg|"Man Hole Door" at Girard College, Philadelphia, constructed in the 1840s

File:Openchannelflow-domed-metering-manhole.JPG|An open packaged metering manhole made of fiberglass before installation

File:Sasa manhole cover.jpg|Manhole cover in Kibbutz Sasa, Israel

File:HAIFA DOWN TAWN.jpg|Manhole cover in downtown of Haifa, Israel

File:Golden manhole cover Tel Aviv.jpg|Painted gold Manhole cover in Tel Aviv, Israel

File:Gas manhole in Dnipro.jpg|Small gas manhole in Ukraine.

</gallery>

See also

  • Packaged metering manhole
  • Sanitary manhole

References

  • Isles, Paul (2010). "Dover Engineering Works". Dover Life Magazine

Further reading