A manhole, also known as an inspection chamber, is an access point to an underground drainage system. Access is necessary to ensure the drainage system can be cleaned, cleared and inspected at will.
Manhole chambers are typically installed where a branch pipe joins a main drainage run in the drainage system, when there is a straight run of piping that is over 22 metres long, or when a drainage pipe changes direction horizontally by more than 30 degrees.
They are covered by manhole covers to stop people falling into them by accident, or entering them without authorisation. Inside older manholes are steps to allow for easy access to the underground space. In manholes where access is required, ‘confined space’ risk assessments and method statements have to be prepared.
However, because smaller, plastic inspection chambers are designed so that physical entry is not required, they often do not contain steps.
Manhole and inspection chamber guidance is governed by Building Regulations.