Comments for So Just Why Are Manhole Covers Round?

Comment from john neil on 2009-11-13

2009-11-14T02:02:37Z

the simple answer is round hole square peg.....
other answers ease of replacing in hole ..equal size means no manouvering to match hole .it simply drops in.
there are many answers to this question.......

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Comment from Just J on 2009-09-18

2009-09-18T13:18:59Z

Leo

As your father claimed they were easier to manufacture round, and that suggestion was the *only* reason begs the question *why* are they easier to manufacture that way?

Any idea?

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Comment from cameron on 2009-08-23

2009-08-24T01:27:58Z

many of the above answers are true and correct when they are brought together. yes the hole is round and yes the seal is better and yes it cannot fall into the hole. there are other factors too, such as a circle being the strongest shape therefore alowing maximum strength and being able to cope with the huge volume of weight and pressure from above the street. the portability aspect of being able to manouvre the cover due to its rondness is also true. therefore manhole covers MUST be round!!!! and no i did not miss the point of the question

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Comment from Keenan on 2009-08-15

2009-08-15T08:45:22Z

Well, I never really thought of that until I read it.

But it totally makes sense, ok round the cover is larger than the opening! So it can't fall in, even if you rotate it or turn it on it's side.

But... If you use a rectangle for example, still the same effect, but if you turn it on it's side or rotate it, it could fall in, or not line up.

Other "Ideas" around the Manhole.

[Content copied from Wikipedia removed.]

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Comment from Ali Ree on 2009-06-08

2009-06-08T17:22:16Z

I too, knew the answer would be simple...because holes are round....more specifically manholes are round...does that mean I'm simple???/

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Comment from Bart on 2008-12-08

2008-12-09T02:11:09Z

A round manhole cover will not fall through a round manhole because the actual circumference of the frame it sits in is slightly greater than the circumference of the whole itself, thus allowing it to lay flush with the street without falling into the whole. No matter how you position the cover, its smallest diameter (all diameters) is larger than any diameter of the hole.

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Comment from vivebrulee on 2008-10-16

2008-10-16T10:52:17Z

Because round seals in moisture and hence the smell better, than straight edges. The edges would not seal as much during expansion and contraction. Ever wonder why tumblers and dive watches (mostly) are round too? That's why.

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Comment from Adri Malia on 2008-09-17

2008-09-17T10:47:24Z

Because they are not square.............

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Comment from mark on 2008-07-16

2008-07-16T09:09:30Z

Manhole covers are round simply because the friggen manholes are round. Why would you make a cover different from the opening?

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Comment from Rick on 2008-06-02

2008-06-02T10:42:15Z

A round manhole cover would not fall through its circular opening????

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Comment from Erika on 2008-04-21

2008-04-21T21:51:13Z

I was asked that today in an interview....lol

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Comment from terry coon on 2007-10-27

2007-10-27T15:18:41Z

Why won't a round cover fall in the hole? Seams to me it would unless the circumference of hole is less than that of cover.

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Comment from Jennifer on 2007-09-19

2007-09-19T18:42:23Z

This is a good question to use in an interview with a future reference desk librarian. They get questions along these lines all day!

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Comment from Cecelia Nosa on 2007-05-08

2007-05-08T20:35:07Z

When I was asked why Manhole covers are round the first thing that came into my head was because men are not square, silly but true.

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Comment from Carrie on 2006-12-06

2006-12-06T18:53:19Z

My first thought was that if the man in the manhole had to get equipment down there (wires, tools, etc.) the items would not get stuck as easily on a rounded surface. A square surface has corners that items would get caught on. Now that I'm thinking about it...boy am I missing something here!!!

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Comment from Moe on 2006-05-29

2006-05-29T23:59:59Z

I grew up in Nashua, NH and remember manhole covers there were triangular. I was told it was because they wouldn't rattle.
(Should it be personhole cover?)
;-)

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Comment from e hansen on 2006-05-24

2006-05-24T21:13:46Z

The shaft leading up to the manhole is round and as we all know a round shaped 'tube' is not only stronger than a square shaped 'tube' but it also uses less material to manufacture. Think about why submarines are round shaped, they have pressure all around it trying to crush it. The same principle applies to a manhole. Therefore the covers are round. Plus they have the added advantage that they will not fall into the hole like a manhole of a different shape would.

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Comment from Holly Johnson on 2006-04-09

2006-04-09T21:30:35Z

The first answer that came into my mind was, "Because most modern men aren't square." Does that qualify me as logical? By the way, what the f... is a manhole cover, actually?

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Comment from Vance on 2006-04-04

2006-04-04T14:44:56Z

I think if I were asked this question in an interview my response (I'm fairly confrontational) would be to ask the interviewer, what are you REALLY looking for? Abstract thought? Logic? Problem solving?

Ive worked in and around manholes for years and in all parts of the world. I have seen square manhole covers. I have seen square manhole covers fall into holes because they are very heavy, not a little bit awkward, and have a tendency to slide, and the square shape allows for it. I have never seen a square manhole cover fall on anyone and safety is NOT a factor because noone would be working IN a manhole while someone was adjusting a manhole cover above them. Safety IS a factor when the poor schmuck had to lift the thing OUT of the manhole.

I suspect that the reasons that most if not all new manhole covers are now manufactured round are that 1-the cover will never fall into the hole 2-It can be moved fairly easily, 3-The round shape easily facilitates work being performed in the manhole with the most efficient use of space.

Maybe the best interview answer is that if 'I' were developing a manhole that i was going to be required to use on an everyday basis, and considering my work requirements and all other considerations, round manholes would be the logical choice for me. I cant say why others choose to.

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Comment from ruchi on 2006-01-24

2006-01-24T15:02:11Z

Round manhole covers can be tightened to the manhole by providing grooves or threading to it.

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Comment from Stacy on 2006-01-21

2006-01-21T22:13:55Z

Why does it never occur to anyone that manhole covers are round because the manholes themselves are round?

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Comment from Jennie on 2006-01-06

2006-01-06T22:32:53Z

In Hong Kong, I've witnessed countless square manhole covers, as well as those that consist of 2 triangular covers that make up the square shape. I am totally convinced by the logical (+ health & safety) fact that round covers could not fall into the hole, among others. Though I am not too sure giving this answer would guarantee a total success at the interview - interviewers look for your reasoning right? So simply saying I've found opinions that say so isn't gonna impress.

Try this instead: How many trees are there in England? (I was asked that yesterday)

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Comment from John Hills on 2005-11-28

2005-11-29T05:35:12Z

The question implies that a manhole cover is round universally and eternally. This could never be proved. The question should not have been asked.

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Comment from Mattrix on 2005-11-28

2005-11-28T15:56:53Z

Geoff... Perhaps it should...

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Comment from Geoff on 2005-11-27

2005-11-28T00:35:29Z

My manhole doesn't have a cover...

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Comment from Jeremy Smith on 2005-10-15

2005-10-15T17:35:17Z

One reason sewer covers are round is that no matter what position it is in, it won't slip through the hole. Circles and squares are not made equally because if you turn a square sewer cover perpendiculer to the ground and diagonally to the hole, and let go, you will hear a clang or possibly a crash as the thing hits the bottom of the sewer.

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Comment from Monica Rodriguez on 2005-10-01

2005-10-01T13:39:35Z

I am posing this question as a mystery for my geometry students to solve. I am not allowing the use of the Ineternet, but I want to give them clues to solving the mystery. Can you tell me how heavy most manhole covers are?

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Comment from Phil on 2005-09-27

2005-09-27T18:40:36Z

I just asked someone this question at an interview (I know, I should be shot). The reply was "what's a manhole cover?". Serves me right, huh?

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Comment from Elphaba on 2005-09-05

2005-09-06T00:42:56Z

You can fit the same size fat guy into a circular hole and a square hole, so why not just save material and make a circle. Ehehe...*picturing a fat guy jumping into manhole*

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Comment from qUARKA on 2005-08-16

2005-08-16T21:18:34Z

Because they are manufactured in that way. Next question is "Why factories do that?" I do not know. I don't have a degree in this industry.
So how? :)

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Comment from EC on 2005-08-04

2005-08-04T22:48:37Z

I'll ask you next time I need a manhole designed! :)

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Comment from Greg on 2005-06-30

2005-07-01T05:27:57Z

Note: This has nothing to do with a person being a Square.

Circles and Squares were created equal.

Have a happy yellow "smiley face" sticker kind of a day!

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Comment from JP on 2005-05-27

2005-05-27T12:31:38Z

Leo

I think its a crime you are "hawking" this crap for $20 on the net.

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Comment from Katherine on 2005-05-24

2005-05-24T14:46:03Z

I think I had a very unusual answer. My ex used to work for the Parks Dept. and one day was pulling a lawn mower behing him. He was not looking and actually fell into a manhole. Therefore it is to keep people from falling in. Next, my 10yr. old son had a friend who said he had thrown his Aladdin's lamp into the sewer. When my son tried to take the man hole cover off he smashed his fingers. Next, to keep children from getting in. And third the best I could come up with is to let people get in there with the rats and stuff to work on pipes and things. 1,2,3 had a reason for each. We'll see if I get the job. :-)

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Comment from Jamie on 2005-04-03

2005-04-04T00:31:32Z

Yes its also because Circles are one of the strongest shapes in the world.

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Comment from Joe on 2005-04-03

2005-04-04T00:28:33Z

Does it have anything to do with the a circles strenght?

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Comment from Leo on 2005-04-01

2005-04-01T22:13:59Z

I think twice about working for someone who's still actually using this question in an interview.

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Comment from marysh on 2005-04-01

2005-04-01T22:07:43Z

Hi,
I was asked this question in an intreview today, and asked to give 3 answers. I could think of only one, and so was asked to think of more answers, andd so I looked up this website!

thanks
Mary

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Comment from Damaraju Pawan Kumar on 2004-12-13

2004-12-14T06:55:08Z

Its not that man holes should be round . there are many shapes which work with same efficiency.

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Comment from shokri on 2004-12-04

2004-12-04T20:14:15Z

No,t leat the cover go insaed the hole

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Comment from pati on 2004-06-11

2004-06-11T21:47:12Z

Ha ha Hugh,
I think thats a very clever response!!!

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Comment from Hugh on 2003-11-24

2003-11-24T22:10:09Z

The Dean of the School of Industrial Engineering at Purdue asked our Sr. class the same question. I did NOT gain points by answering "because the holes are round." He was not amused.

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Comments for So Just Why *Are* Manhole Covers Round?

Comment from john neil on 2009-11-13

Comment from Just J on 2009-09-18

Comment from cameron on 2009-08-23

Comment from Keenan on 2009-08-15

Comment from Ali Ree on 2009-06-08

Comment from Bart on 2008-12-08

Comment from vivebrulee on 2008-10-16

Comment from Adri Malia on 2008-09-17

Comment from mark on 2008-07-16

Comment from Rick on 2008-06-02

Comment from Erika on 2008-04-21

Comment from terry coon on 2007-10-27

Comment from Jennifer on 2007-09-19

Comment from Cecelia Nosa on 2007-05-08

Comment from Carrie on 2006-12-06

Comment from Moe on 2006-05-29

Comment from e hansen on 2006-05-24

Comment from Holly Johnson on 2006-04-09

Comment from Vance on 2006-04-04

Comment from ruchi on 2006-01-24

Comment from Stacy on 2006-01-21

Comment from Jennie on 2006-01-06

Comment from John Hills on 2005-11-28

Comment from Mattrix on 2005-11-28

Comment from Geoff on 2005-11-27

Comment from Jeremy Smith on 2005-10-15

Comment from Monica Rodriguez on 2005-10-01

Comment from Phil on 2005-09-27

Comment from Elphaba on 2005-09-05

Comment from qUARKA on 2005-08-16

Comment from EC on 2005-08-04

Comment from Greg on 2005-06-30

Comment from JP on 2005-05-27

Comment from Katherine on 2005-05-24

Comment from Jamie on 2005-04-03

Comment from Joe on 2005-04-03

Comment from Leo on 2005-04-01

Comment from marysh on 2005-04-01

Comment from Damaraju Pawan Kumar on 2004-12-13

Comment from shokri on 2004-12-04

Comment from pati on 2004-06-11

Comment from Hugh on 2003-11-24

Comments for So Just Why Are Manhole Covers Round?