When to Use Domed Tops for Manholes

Manholes are one of the best tools for accessing a flume or vault that measures the flow rate of an underground wastewater channel. They come in various sizes and lengths, making it easy for workers and monitoring agents to reach the measurement device no matter how far down it is. The question is, what kind of top is best for the manhole? While there are several options available, domed tops are the most popular. Learn when to use domed tops for manholes.

Domed Top Benefits

It’s no accident that domed tops are the most popular style of top for manholes. They not only keep the access way clean, but they make it as easy as possible for the underground flume to be accessed. This is largely due to the manhole sticking out about a foot above the ground, allowing any user to use the lip of the manhole itself as a handhold.

While manholes are useful for allowing people access to an underground flow channel, outside surface water needs to be kept out. Fortunately, the domed design lets gravity take care of those efforts for the most part. Water will flow down the sides of the manhole cover rather than pool on the top.

Exposure to Traffic

Generally speaking, it’s best to avoid domed tops in any areas that get a lot of traffic. Given the fact that they sit about a foot above the ground, cars can be seriously damaged if there’s a collision, though the manhole itself will likely be fine as domed tops are tested to withstand the weight of a car. If you do have to install one in an area with high vehicle traffic, it’s always best to install bollards or some kind of posts to keep the traffic away from the manhole itself.

For similar reasons, domed tops don’t work very well when used in areas that have a lot of foot traffic. This kind of manhole cover can be an obvious trip hazard even when properly marked. Instead, you may want to consider using a hatch covering that’s equal to the grade of the surrounding surface. If there’s no choice but to install one in a pedestrian area, it’s always best to mark it with brightly colored signs.

Lid Security

If you’re looking for a manhole cover that can safely be held open when in use, domed tops work well with gas struts. These devices allow the top to easily be opened and held in place while in use. You just have to remember that size does matter. Always match the strut with the size of the top, or else it will exert so much force that closing the top when you’re finished will be extremely difficult. 

Keep in mind that domed tops aren’t designed to be gas-tight or watertight. That’s why they’re set above grade so any pooling water on the ground will have to get significantly deep before affecting the manhole. If you do need the top to be watertight, you’ll have to opt for a more customized, often flat design.

Manholes From Tracom

Now that you know when to use domed tops for manholes, it’s time to get one of your own. That’s where Tracom can help. Get in touch with our team today to get started designing fiberglass manholes with the appropriate tops perfectly suited for your flow channel specifications.

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