Why are manhole covers round


The best correct answer as to why any given manhole cover is round is because the pipe which it caps is round also a round manhole cover won’t fall into a hole because it was rotated the wrong way so it’s safer[6]. A round manhole cover can’t fall through its circular opening because no matter how you position it, the cover is wider than the hole[4]. Therefore many manhole covers are round so they don’t need to be rotated[3].

Covers are round because the hole is round since a manhole covers is quite heavy (200 to 300 pounds) that’s pretty helpful[7]. Thus it is easier to dig and maintain round holes and because it’s round it can be more easily transported[3]. Another secondary reason manhole covers are round might be for the ease of putting the manhole cover in[7].

A number of possible explanations for why manhole covers are round include but perhaps the biggest reason that manhole covers are round is that round covers can’t fall through a circular opening[4]. Round manhole covers & frames however not all manhole covers lead directly down to round holes, they often lead to a larger cavern easier to move round manhole covers around by rolling them[2]. A cylinder is the optimal shape for stacking, loading and transporting manhole covers, as well as being easier to install and maintain[2].


  1. https://www.livescience.com/32441-why-are-manhole-covers-round.html
  2. https://www.envirodesignproducts.com/blogs/news/the-surprisingly-technical-reason-that-manhole-covers-are-round
  3. https://careercenter.bauer.uh.edu/blog/2021/09/20/sample-interview-questions-why-are-manhole-covers-round/
  4. https://www.mentalfloss.com/article/60929/why-are-manhole-covers-round
  5. https://www.forbes.com/sites/meghancasserly/2011/07/27/the-10-toughest-interview-questions/
  6. https://www.glassdoor.com/Interview/Why-are-manhole-covers-round-QTN_2480.htm
  7. https://untappedcities.com/2021/02/22/why-are-manhole-covers-round-an-official-answer/
  8. https://www.careerfaqs.com.au/careers/interview-questions-and-tips/job-interview-question-and-answer-why-are-manhole-covers-round
  9. https://www.quora.com/Why-are-manhole-covers-round

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