• Manholes are underground chambers typically constructed in cylindrical or rectangular profile on regular intervals on sewage lines or other water lines, generally changing the direction of flow passing through or providing sudden changes in flow level as well as allowing personnel access in case of blockages, and manhole covers are objects used to cover manholes against hazards.

Manholes are underground chambers typically constructed in cylindrical or rectangular profile on regular intervals on sewage lines or other water lines, generally changing the direction of flow passing through or providing sudden changes in flow level as well as allowing personnel access in case of blockages, and manhole covers are objects used to cover manholes against hazards.

They are used to carry out inspection, cleaning and removing obstruction in the sewer line. Manhole allows joining of sewers or changing the direction of sewer or alignment of sewer or both.They allow the escape of considerable gases through perforated cover and thus help in ventilation of sewage.They facilitate the laying of sewer line in convenient lengths.

The term manhole comes from the 19th century and originally referred to a small access hole in the top or side of a boiler that was covered with a heavy metal plate bolted in place. These holes were not meant to provide access for a man to pass through, but for an arm and hand to reach the inner parts of the boiler. “Man” in this case refers not to the gender of the worker, but is from the root word that means “hand,” as in the word “manual.” Indeed, some old boiler manuals use the words “manhole” and “handhole” synonymously. Sewer manholes were probably so-called as an extension of the general term that meant “an access hole” and the gender-specific meaning followed naturally, albeit somewhat erroneously.