Manholes – Types, Purpose, Construction & Maintenance


Workers use manholes to access the underground sewer and water systems, which have been laid underground in many cities, towns, and villages worldwide.

They usually have a cover that needs to be removed so that workers can safely get down inside the manhole and do their job of maintaining or repairing the systems below.

But before anyone can safely open up and enter manholes, you’ll need to know more about them and their main purposes, along with some of the different types of manholes you might encounter in your day-to-day life.

Today we’ll learn about three different types of manholes and how each one can help you achieve its goal for utility maintenance.

What Are Manholes?

Manholes are underground structures that give access to cables, pipes, wires, and sewers. They also come in handy when maintaining or repairing these things.

The purpose of these covers is pretty obvious from their name – they serve as an opening from a manhole into an underground chamber that contains one or more utility lines.

Whether or not you know it, you’ve likely seen manholes in your daily life. Manhole covers are used to cover small underground access points that allow workers to travel from one point to another safely.

Although manhole covers are often forgotten about once they’re put into place, they are crucial for everyday safety and underground utility maintenance.

Underground utility systems play a key role in helping cities function, so there needs to be a safe way for workers to get around when it comes time for repair or construction projects.

How Are The Manholes Made?

In general, manholes are manufactured from concrete. However, several different types differ depending on their purpose. Here’s an overview: Round – The most common type is round and has an internal diameter of about 15 inches (38cm).

They’re relatively small compared to other types, making them easy to handle during construction work. If you’re renovating your house, you might need larger ones for future use.

Usually, cast iron or ductile iron (steel) manhole is made by machine casting methods. The machines are as follows: sand-making machine, melting machine, pouring machine, and surfacing-grinding machine. They are placed in a row for production.

According to different specifications, the standard manhole is divided into two types: ordinary type with lifting frame and special type without lifting frame; also divided into dry pipes and wet pipes.

The dry pipes watercourse has no contact with the underground water. In contrast, the wet pipes have the watercourse in contact with underground water.

In addition, the manhole can be produced in different shapes such as round, oval, square, polygonal (such as a triangle), etc.

Different Types Of Manholes

You might think that all manholes are essentially similar; after all, they’re essentially just holes in a road. But, as it turns out, there are several different types of manholes for various reasons—and even just in terms of location. Based on the depth of a manhole, it has been categorized into three parts- shallow, normal & deep.

1. Shallow Manhole

A manhole having a depth of up to 90 cm is termed a shallow manhole. It serves as an inspection chamber at the start of a branch sewer, and the cover is light in weight.

2. Normal Manhole

A manhole with a depth of 90-150 cm is categorized as a normal manhole, and it is covered with a heavy cover.

3. Deep Manhole

A deep manhole has a depth greater than 150 cm. The size of a deep manhole is also big, according to the size of the facility. It is also facilitated with a permanent ladder.

Purpose Of Manhole

The different types of manholes have different purposes.

1. Sanitary Sewer Manhole

It provides the entry or exit to a sanitary sewer.

2. Storm Sewer (also known as catch basin) manhole

It is used to enter or exit a storm sewer. The opening is designed with a lip on which water can flow, so rain will naturally wash any contamination into the storm sewer instead of entering buildings.

3. Utility Manhole

Also called fire protection system manhole. It is used for locating buried utility lines such as gas, water, cable TV, telephone systems, and others for maintenance work.

Utilities generally don’t place their own service pipes in underground concrete vaults—this allows customers access to these facilities if maintenance or repair is needed while providing physical security.

How To Construct A Manhole?

The type of manhole determines how it is constructed. If a manhole needs to support heavy loads, a metal grate or surface will hold up to those loads.

In contrast, if it only needs to resist light vehicle traffic, its surface will be lightweight, like concrete. All manholes are also waterproofed so that water cannot seep into them.

To do so, they are either covered in tar or filled with grout as an extra layer of protection against rainwater. However, holes are left on top of some sidewalks for drainage purposes when grouting is used instead.

Hire a contractor to install new sewers and other underground infrastructure; they will likely have in-house teams capable of building manhole covers as well.

Manhole covers can be metal or plastic, but most are reinforced concrete. Once you’ve got your concrete formed into a manhole cover, it’s not that hard to install one.

Manhole Construction Material

The manholes are available with the following material. The choice of material depends upon the use, location, and cost.

  • Plastic Manholes
  • Precast Concrete Manholes
  • Fiberglass Manholes
  • Mild steel Manholes
  • Brick/Stone Masonry Manholes

Maintenance Of Manhole

When something goes wrong in a sewage system, manhole problems are usually to blame. If a manhole is not properly maintained, it could cause flooding and contaminate an area with potentially dangerous germs. There are two major aspects to consider for manhole maintenance- manhole cover and cleaning.

1. Manhole Cover

Even though many manhole covers are made from durable material such as cast iron, they still require maintenance. If a manhole cover is damaged, it should be repaired or replaced, and these repairs should be done immediately so that they do not pose any safety hazards to people or vehicles.

The covers can become dislodged by trash truck wheels or other heavy vehicles driving over them, and they can also lose their lids through corrosion or wear-and-tear. Also, each manhole should have its own unique number placed on it to identify quickly if an issue arises.

In most cases, road workers will use chisels to remove old numbers off manholes before attaching new ones onto them. It is also important to note that some cities also mark specific areas as hazardous by placing signs there.

2. Cleaning

It is very important to keep a manhole clean. If it gets blocked by any object, it may lead to serious consequences like blockage of water supply lines or sewer lines which can cause serious health problems.

Cleaning a manhole is not an easy task, and it takes several hours as you need to go deep inside it. Depending on its depth and other factors, it can take six to twelve hours to complete cleaning.

Also Read

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