Manholes are installed in sewer lines for the access of:

The installation of manholes in sewer lines is primarily for the access of personnel and materials. Manholes serve as entry points that allow maintenance workers to access the sewer system for inspections, cleaning, and repairs. This accessibility is crucial for ensuring the smooth operation of the sewer lines and for addressing any issues that may arise, such as blockages or structural problems.

Additionally, materials such as tools and equipment needed for maintenance can be easily transported through manholes, facilitating the work of sewer maintenance teams.

While backflow devices, traffic control devices, and survey equipment may be associated with sewer systems, they do not accurately capture the primary purpose of manholes. Backflow devices are typically installed within the system but do not require manholes for access. Traffic control devices pertain to public safety and roadway management rather than sewer maintenance directly. Survey equipment is often used for monitoring and assessment but does not necessitate the dedicated access that manholes provide in terms of routine and emergency maintenance by personnel.