Are you curious about concrete riser rings and manholes? This curious guide will teach you something you didn’t already know about manhole structures and concrete riser rings you walk past every day.
What Are Concrete Riser Rings?
Concrete riser rings are pieces below the cone shaped manhole covers that are installed as part of a manhole structure to give it the proper height. They come in different sizes and shapes. They also have different functions, depending on their size and shape.
A concrete riser ring is usually used to raise the top manhole cover so that it can be used as an access point to fix any pipes or cables that may be below the ground level. Sometimes, these rings are also needed to accommodate for changes in elevation or slope of the ground.
When Are Concrete Riser Rings Used?
Concrete risers are commonly used in manhole structures for several reasons. However, let’s use a simple example to explain why riser rings are used in manhole structures.
To start, think about your local area. Is it perfectly flat?
In most neighborhoods, there are elevation changes, even if only a few feet.
For many sewer systems today within neighborhoods, they are designed to work best when they are level. So, let’s say one end of your street is seven feet higher than the other end. Ideally, the sewage pipe in the ground would stay level as it goes down your street and feeds into the main system, where a pump will move the waste through the system. Even if the system is designed for slight slope, seven feet is likely too much. And there isn’t just one manhole on the line, there are several. So, if the sewer line is level, the manhole at the lower end is seven feet lower than the manhole at the higher end.
So how do you make up the difference in height for the manhole covers? You guessed it: riser rings!
Now let us give you one more example that you may not be familiar with: New York City.
Did you know that over time the street level in NYC has risen? That’s right! What used to be the first floor for many buildings is now the basement.
So, when they raised the street levels in NYC, they were able to use concrete riser rings to raise the manhole tops to match the new street level without having to complete redo the entire sewer system.
Concrete Riser Rings and Manholes Over the Years
Above we shared some stories about manholes and riser rings to help you better understand why they are used. But did you know that traditional concrete riser rings have issues that make them not very environmentally friendly? Think about it… If an old concrete sewer system cracks (which happens often with traditional concrete systems), then sewage spills where we don’t want it. Gross!
And then those systems need to be replaced, which means digging up the earth, using more raw materials, and creating more waste.
However, just like many things in our lives today, yes, technology is improving even our sewer systems. A recent advancement is polymer concrete, and when used for manholes, riser rings and overall sewer systems, it can save money and the environment because it lasts a minimum of twice as long as traditional concrete. So, we encourage you to encourage your local municipalities to use polymer concrete for their next project.
