Manholes have been in use in the US since about the mid-19th century. While their purpose hasn’t changed for nearly 200 years, their construction and design significantly evolved to reflect the ever-growing needs of the modern world. Today, there are an estimated 20 million manholes throughout the US, most of which are upgraded to the current standards. 

Manhole castings are among those key components that significantly contributed to the modernization of the underground utility systems as a whole – yet, most people are unfamiliar with even the basics of their construction and design. Let’s correct that injustice by familiarizing ourselves with the definition and builds of these essential solutions.

What is a casting on a manhole?

Manhole casting refers to the metal frame and cover (circular, rectangular, or square lid) that sits on top of the manhole shaft, facilitating access to the utility system located underground, such as water, wastewater, telecommunications, gas, and many others.

The reason why it’s called “casting” is due to the method used in its production. The casting process is a manufacturing method where liquid material (in this case, molten metal) is poured into a mold of the desired shape and left to solidify. 

As a result, the cast component gains excellent durability and strength, allowing it to handle heavy loads (such as road traffic) without deforming or breaking – even after decades or, in some cases, centuries of use.

Are manhole lids cast iron?

Historically, most manhole lids, as well as castings, were made of cast iron – and for a good reason. The properties of this material make it an excellent choice for heavy-duty applications:

• Ability to withstand excessive loads and pressures
• High resistance to wear and impact
• Good corrosion resistance (especially when treated)
• Long service life, even in harsh conditions
• Easy to cast into desired shape/size
• Cost-effective option

While cast iron has traditionally been the go-to choice for lids and castings, advancements in manufacturing technologies shifted the focus toward other materials, primarily ductile iron. The reason for this change is twofold:

• Ductile iron is significantly stronger than cast iron while having lower mass. This effectively enables for the creation of thinner and lighter lids, which are not only more manageable for utility personnel but, also, less likely to cause damage to vehicles or severe injuries to individuals in case of accidents.
• Ductile iron is much more flexible than cast iron, making it less likely to crack, break, or deform under impact. This property can be critical in environments where sudden shocks are commonplace, such as industrial sites, heavy traffic areas, or regions prone to earthquakes.

Of course, ductile iron isn’t the only material that is commonly used in the production of manhole covers nowadays. We’re also seeing an increase in the utilization of steel alloys and composite materials, all of which offer enhanced strength, durability, longevity, and weight reduction, while being more cost-effective to manufacture and install than their cast iron counterparts.

Who offers high-quality manhole castings for sale near me?

Are you in the market for different types of manhole castings, modern sewer top hats, or any other water main, sewage, and drainage material? Blair Supply Corp. has everything you need in one place!

With 60+ years of experience, an extensive distribution network, and partnerships with the most prominent manufacturers in the industry, we’re the supplier contractors throughout the US rely upon to facilitate their construction and maintenance efforts.

Whether your project is taking place near Watertown’s Jefferson Community College or elsewhere in the nation, you can rely on us to provide you with the top-quality materials where you need them and when you need them – every time. Contact us today!