Ever wondered how people manage to work under the bustling city streets? Well, to get down there workers use over 20 million manholes in the USA alone to reach every inch of underground piping.
Precast concrete manholes are an integral part of our infrastructure, helping to keep roads safe and traffic flowing. Yet, these manholes are also prone to cracking and breaking down over time, leading to costly repairs and downtime.
There are some materials used to construct precast manholes including steel, iron, fiberglass, plastic, and concrete. Each has its own advantages and disadvantages. Which is best?
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What Is a Manhole?
A manhole in the ground is a hole that allows access to underground utilities. A sewer manhole is usually located at street level. Yet, it can exist anywhere from basement floors up to rooftop levels.
A typical manhole consists of two parts. First, the cover which sits on top of the opening, and the base which supports the entire structure.
Inside a manhole, a grate covers the entrance so that people don’t fall inside by accident. There may also be stairs or ramps built around the perimeter of the manhole to allow easy access.
Some types of manholes have lids that close off the opening. Others remain open with grates placed above them.
The size of a manhole varies depending on what you need it for. Smaller ones might only accommodate one utility line whereas larger versions could hold many lines.
Types of Manhole Covers
There are many types of manhole covers and materials used to make them. Here are some of the most popular ones.
1) Metal Manholes
The most common covers we see today are made from metal. They come in various shapes and sizes. These range from simple round holes all the way to complex designs.
These covers are generally attached by bolts or screws. The design is such that they fit snug against the sides of the manhole. This helps prevent leaks and keeps debris away from the interior of the manhole.
2) Concrete Manhole
Another very common material used to build precast manholes is concrete. Concrete manholes tend to weigh more due to the added weight of the concrete itself. Further, concrete tends to crack much faster than other options, particularly under high stress.
3) Fiberglass Manhole Cover
Fiberglass manholes exist for areas where corrosion is likely to occur. Fiberglass is very durable and resistant to damage caused by weathering.
It comes in several different colors and patterns. Fiberglass manhole covers are available in both flat and curved styles.
4) Plastic Manhole Cover
This type of cover is becoming more popular. That’s because it is lightweight and inexpensive compared to traditional options.
Plastic manhole covers are often used in limited spaces since they take up little room. Yet, these covers do not last as long as other options and you should replace them often.
Choosing Precast Manholes Today
When choosing your precast manholes, consider how large an area needs covering. You should also consider whether you want something decorative or functional.
And, consider whether you plan to use it indoors or outdoors. The best thing about using a precast manhole cover is that it doesn’t need any special tools to install. You bolt it into place and then fill the hole with soil once it’s finished.
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