Manholes are the most frequently used underground structures for utility maintenance, allowing access to installed pipelines. It is an important part of the sanitary system and water supply. A manhole is an inspection chamber that provides access to utilities such as sewer, drainage systems, water supply systems etcetera.it is generally a structure constructed and placed underground for inspection or to provide connectivity of pipes.it is a very useful structure in buildings and has many advantages. Let’s look at a comprehensive guide to manholes in Kenya.
Manholes are primarily built for trenchless sewage system rehabilitation, drainage systems inspections, blocked line cleaning, and maintenance requirements. They typically consist of an inspection point accessible to vertical circular chambers with a range of sizes and depths
Uses of manholes in kenya
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Cleaning
Manholes placed in regular spacing are used for cleaning pipes
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Inspection
Manholes are used as inspection chambers, when there are long pipelines, they are required for various purposes.
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Maintenance
Manholes are required to do the maintenance on the pipelines that lay underground. They may be placed to transfer liquids or for electrical work.
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To seal foul gases escape
When the sewer lines are running from starting point to the end, there will be leaks in foul gases. Manholes are used to seal these foul gases. The covers have perforations that allow the unpleasant gases to escape providing the underground sewage system with effective ventilation.
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To join two lines
When pipelines are laid, they need to connect in order to maintain continuity. Can be either a sewer line or a water line. The change of direction or the alignment of sewers can be performed with the help of a manhole.
Types of manholes in kenya
There are numerous kinds of manholes for a variety of reasons. Manholes have been classified into three different categories based on their depth.
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Shallow manhole
A shallow manhole is between 75 to 90cm deep and is built near the beginning of a branch sewer in a place with little traffic.a small cover known as the inspection chamber is attached to the shallow manhole.
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Normal manholes
These are available near the sewage line and have a thick cover over them .they are typically 150cm deep and square in shape.
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Deep manhole
A deep manhole has a hefty cover at the top and is at a depth greater than 150cm. The capacity for growth is greater as is the ability to descend. Such a manhole is smaller at the top because the size is larger at the bottom.in order to allow descending to the bottom, steps are installed on one of the manhole’s vertical walls.
Materials used in the construction of manholes in Kenya
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Precast concrete
This is a traditional method of constructing manholes. The manufactured precast manholes are assembled on-site, hence this method ensures quality and facilitates faster installation. Increased durability with a long lifespan is the reason for their increased popularity.
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Fiberglass manholes
The fiberglass manhole is manufactured using fiberglass technology and is simple to handle and install. It significantly weighs less than a concrete manhole. It is also environmentally friendly and long-lasting in nature.
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Plastic manholes
Polyethylene is the material used to make plastic manholes.it is sustainable and environmentally friendly and it has no adverse impact on the soil where it is installed. Such manholes are manufactured with accessories like covers and ladders.
Key takeaway
Generally, manholes in Kenya are provided where there is a change in the alignment of the sewer, change in the direction or grade of the sewer, change in the size of the sewer, and at the junction of two or more sewers.
