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Manhole covers are found everywhere—on city streets, in residential neighborhoods, and even on your own front lawn. Despite their frequent presence, manhole covers are rarely given much attention by the public. Regardless, these round or square caps play an essential role in society that is difficult to ignore.
The development and use of manhole covers are complex processes that require some knowledge to practice. In this guide, we’ll delve deeper into manhole cover types and how to choose the right manhole cover for your needs.
What Is a Manhole Cover?
A manhole cover is a removable lid that sits over a manhole—a deep shaft that typically leads to public sewer systems and utility vaults, providing technicians and workers with easy access to repairs and maintenance. It also serves as a safety precaution for cars and pedestrians walking by.
Most manholes are round to hold against the compression of the earth, but some are square or rectangular to make it easier for machinery to access the utilities below. The shape and dimensions of manhole covers are engineered based on surprisingly fascinating and technical reasons: geometry, functionality, safety, and economics.
How to Access a Manhole
Using the right tools and adhering to safe work practices around manholes is crucial.
On each manhole cover is a keyway, in which maintenance workers can insert steel manhole keys, or “manhole hooks,” to open and gain entry to the shaft. As a safety precaution, a manhole cover is often too heavy to lift by one person, so the cover will usually have two keyways requiring two workers facing one another to lift up the cap together. A manhole hook with a wide handle helps make the removal and replacement process easier by taking some of the pressure off the worker’s back.
To ease the amount of physical stress and strain, the worker can also use a manhole cover lifter to pry open the shaft. A manhole cover lifter can range from a simple pry bar to a contraption involving wheels and a magnet, enabling one worker to do the job on their own.
Types of Manholes
Manholes typically fall into three categories depending on their depth—shallow, normal, and deep. The depth and location of the manhole then determine the manhole cover size, shape, and material.
With only two to three feet in depth, “shallow” manholes have lightweight caps and are also known as inspection chambers. These manholes are typically located at the start of a sewer or stormwater branch in areas with less heavy traffic.
Located in a sewer or stormwater branch, normal manholes are usually three to five feet deep. In terms of the average manhole cover, round is the most common shape, but “normal” manhole covers are often square or rectangular. These shafts are wide enough for the average person and even light machinery to fit through.
A “deep” manhole is classified as any manhole that has a depth of more than five feet. These manholes typically have heavy-duty cast-iron covers and are commonly located on city streets or public sidewalks as an added safety measure. A ladder is usually installed to allow access for maintenance workers underground.
What Are Manhole Covers Made Of?
Although manhole covers may seem simple at first glance, there are intricate details involved in their manufacturing and production. The materials that manhole covers are made from are determined by their intended purpose—or, more specifically, over which manhole they will be placed.
Considered the strongest and most durable materials for manhole covers, ductile and cast iron have been used by manufacturers for centuries.
Due to its capacity for heavy loads, this type of sewer cover is normally placed in high-trafficked areas like highways. Ductile and cast iron manhole covers are created to hold maximum weights of up to 90 tonnes and are most commonly placed over deeper shafts.
Due to its resistance to corrosion and degradation, manhole covers made from polyethylene material (plastic) are considered highly durable. Plastic manhole covers do not corrode and contaminate the surrounding soil with toxic chemicals. Therefore, they require very little maintenance and rarely need to be replaced. Although plastic caps generally last longer, they are usually placed in pedestrian areas like gardens or walkways, as these covers are more suitable for lighter loads.
Quality steel manhole covers are fabricated and galvanized for optimal use, commonly placed in pedestrian areas like domestic driveways, walkways, and even indoors.
Usually created for lighter loads, these manhole covers have a sleek appearance. However, heavy-duty steel can make for manhole covers that are capable of handling high-traffic areas, too.
With superior strength and product durability, composite manhole covers are made from advanced fiberglass reinforced plastic materials, making them very lightweight and easy to handle. This reduces the risk of injury during installation, therefore creating safer work practices.
Considering this material’s non-corrosive and non-conductive nature, composite manhole covers can be placed in the harshest of environments. These sewer covers can be used on both pedestrian walkways and moderately-trafficked areas like roadways.
How to Choose the Right Manhole Cover
When choosing a manhole cover and frame, there are several factors to consider. Creating a set budget and conducting measurements of your manhole’s opening is crucial to finding a manhole cover that fits snugly atop the shaft.
Average manhole cover prices can go up to as much as $500, including labor costs. The price of a manhole cover depends heavily on the quality and the materials used. For instance, plastic and fiberglass are relatively inexpensive materials with many benefits but are unable to support larger weight loads.
However, depending on the size and project, good-quality manhole covers can still be found at affordable prices.
Knowing the size of the manhole is especially important when looking for a cover to match. The sewer cap cannot be too small, as it runs the risk of falling into the shaft. Although it can be tempting to use a cap that is wider than the manhole itself, it is best practice to use a manhole cover and frame that matches the shape and dimensions of the opening.
Manhole cover dimensions are the same as those of the manhole cover’s opening. However, the frame should also be considered, as the dimensions may increase after installation. For instance, a round manhole cover with dimensions of 24” wide x 18” deep will have wider dimensions when the frame is added.
Manhole covers range from lightweight to medium-duty and heavy-duty. The weight of a manhole cover can be determined according to its place in the classification system. The manhole cover weight classifications are as follows:
- A15 = For use by pedestrians and cyclists only
- B125 = Occasional light traffic, including access-only routes, and driveway duty
- C250 = Cars and vans with slow movements, such as in car parks
- D400 = Heavy, fast-moving traffic, especially on main roads
- E600 = Heavy-duty plant traffic with solid tires, such as forklifts in areas with warehouses and docks
- F900 = For areas with high wheel loads, including airports
Which Manhole Cover Fits Your Needs?
When determining which type is suitable for your project and needs, you should consider the manhole cover dimensions and weight, as well as further equipment like manhole cover lifters to help simplify the installation or moving process. Whether you have a round manhole cover or a square one, they all serve the purpose of keeping people safe from harm and protecting underground utility systems.
With so many types of manhole covers to choose from, it’s easy to become confused as to which one is going to fit your budget and offer you the most benefits. At Enviro Design Products, we are dedicated to providing you with top-quality manhole covers that are suitable for commercial or residential use. Visit our shop to browse through a wide range of manhole covers and specialized accessories to enhance utility.