What you Should Know about Manholes


A manhole is an access point to an underground network lime a drainage system. A sewer or drain manhole makes it possible to inspect, survey, unblock, clean, and repair the underground pipes. Building regulations govern the manhole’s guidance on the design, location, and structure.

Moreover, manholes are essential temporary storage point for water as they let water build up in the drainage instead of flood out straight away. As drainage engineers work on pipe systems, they may block a pipe and use the manhole in the same way for storing wastewater before they allow it to flow away after the completion of the drainage task.

Purposes of Manhole Covers

Manhole covers protect the manhole chambers. Manhole covers can be made from various materials such as steel, recycled plastics, and concrete. But, compared with other manhole materials, plastic manholes are extremely resistant to corrosion. They have various purposes including the following:

  • Preventing people from falling down the manhole or entering the drainage system without permission.
  • Preventing debris and objects from getting into the drainage system as they could cause a blockage.
  • Preventing surface water from getting into the drainage system that could cause the pipes to become overfull during heavy rain.

What’s Under the Manhole Covers

A number of manholes are just a few inches or two feet deep. At their bottom, it is common to see the bottom half of a pipe, which is often made from clay, running off into openings such as the train tracks entering a tunnel. Manholes above a drain pipe junction will have more complicated pipe arrangement. Sometimes, manholes are likely to result in much deeper drains and sewers. Bigger manholes may be protected by a steel security grill.

Things that Could Go Wrong with Manholes

Manholes can experience various issues such as:

  • Wrong manhole location. A manhole might be installed in the wrong location. As a result, there might not be one in a location needed to perform a drainage inspection, unblock a drain, or clean a sewer. This could be because of an outdated drainage system that cannot cope with subsequent development.

  • Buried or built-over manhole. To deal with this issue, the manhole should be excavated to gain access to a certain point in the drain. Another way is to create a new drain access point at another location.
  • Unstable manhole. This can be a result of materials deterioration, tree roots action, or ground movement. In this case, it is imperative to repair or even replace the manhole.

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