Components, systems and materials › Water and drainage components › Manhole
Manhole
What it is
A manhole is a chamber built on a sewer or storm drain line that gives access for inspection, cleaning and joining of pipes.
Where it is used
Sewers and drains at every change of direction, gradient, pipe size and junction, and at intervals along straight runs.
How it works
Pipes enter and leave at the base, where a shaped channel (benching) carries flow smoothly through. The shaft above gives a person or equipment access. Covers and frames carry traffic loads at road level. Drop manholes carry a high incoming sewer down to a lower one without damaging the chamber.
Types
- Shallow and deep manholes
- drop manholes
- brick, cast-in-situ and precast concrete manholes
- plastic inspection chambers for small house drains
Materials
Brick, concrete, iron covers.
Spacing, sizes and drop arrangements follow the CPHEEO Manual on Sewerage and Sewage Treatment Systems. Covers are selected for the traffic class of the road. Chambers are checked for soil and groundwater pressure and for buoyancy where groundwater is high.
Installation and QA steps
- Excavate and support the trench
- Cast the base and form the benching to the pipe inverts
- Build or place the shaft rings with sealed joints
- Fix the cover frame at road level
- Test for watertightness
- Infiltration of groundwater through joints
- Corrosion of concrete by sewer gases
- Broken or missing covers, a serious hazard
- Frames set below road level causing potholes
Codes cited
- CPHEEO Manual on Sewerage and Sewage Treatment Systems (2013) (India): Central government manual for sewer networks and sewage treatment plants.
Cited by number only. We do not reproduce code text, tables or figures.
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