×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

wht is the purpose of holes in man hole covers

wht is the purpose of holes in man hole covers

wht is the purpose of holes in man hole covers

(OP)
what is the purpose of holes in manhole covers?

RE: wht is the purpose of holes in man hole covers

I thought the holes were called pick holes for that purpose.

RE: wht is the purpose of holes in man hole covers

They could also be for air ingress and egress if the manhole covers a pit where an air valve on a pipeline is placed. Otherwise the air valve wont function or the cover could be blown off.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

RE: wht is the purpose of holes in man hole covers

For whatever it is worth I believe at one time there was quite a bit of discussion and indeed maybe some practice in areas regarding "holes" in manhole covers (beyond modern "pick holes" in gray or ductile cast iron covers) e.g. as mentioned in ASCE Manual #37, "Design and Construction of Sanitary and Storm Sewers" (1982), e.g. "...ostensibly to aid ventilation". However, the 1982 version of this manual also provided several possible hints as to why this and other publications (e.g. ASCE MOP No. 60/WPCF MOP No. FD-5, "Gravity Sanitary Sewer Design and Construction" 1982) have not really promoted this as a function of manhole covers in recent years. These hints included the following:

1. "At most, a ventilated cover may permit partial drying of the manhole but it cannot affect appreciably conditions in the pipe between manholes."

2. "In exceptional conditions where ventilation may be needed to relieve pressure differences or prevent oxygen depletion, special vents should be provided." (I believe Mr. stanier's application might fit this bill, and I think "special vents" in that context were probably meant to potentially refer to structures beyond simple cored or drilled holes in the cover.)

3. "On sanitary sewers, holes in the covers allow the undesirable entry of stormwater and grit, as well as the mischievous entry of sticks; and they favor the escape of sewer air, causing odor nuisances." (i.e. holes are likely to increase volume to be treated, particularly in low lying areas or areas subject to flooding etc., where alas many sewers are wont to be!)

For these reasons I believe modern trends are more likely to want tighter overall systems and manholes, including covers.       

 

RE: wht is the purpose of holes in man hole covers

Have you ever tried to open a MH without pick holes, alone and only a pick in the car?  

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: wht is the purpose of holes in man hole covers

Many years ago I was told that the holes in gravity sewer lines were there to compensate for for changing flows or levels especially large diameter lines.

Addenda:
In front of the old home place there is 12' diameter brick gravity sewer that comes from Birmingham, Alabama. The manholes are spaced quite close to gather as I could see three standing on sidewalk in front of the house.  While walking to school one morning the air was still enough that you could get whiff of H2S as you passed by a manhole.  That morning as I got to the one in the street in front of the school and about 15' from the manhole there was an explosion in the sewer line which lifted every cover in sight to way above he 50' telephone poles. The one by me came down through the telephone wires and took out about 1/3 of them. from that time on I avoided hanging around any sewer manholes.

RE: wht is the purpose of holes in man hole covers

Regarding:  Many years ago I was told that the holes in gravity sewer lines were there to compensate for for changing flows or levels especially large diameter lines.

The stack vents in the house laterals take care of the venting.
 

RE: wht is the purpose of holes in man hole covers

Individual stack vents do not vent the sewer mains.  

RE: wht is the purpose of holes in man hole covers

Sanitary manholes are no longer constructed with open grates. Since all manholes now are essentially sealed, how would you expect the venting to occur?

Note that gravity sewers do not operate with full pipes, there is air above the fluid.

Note that when you drive down a northern residential street in the winter, you can observe the venting and condenstation.

If you remain unconvinced, perhaps you should consider reviewing a book like Metcalf & Eddy's Collection & Pumping of Wastewater. The link contains a pertinent section discussing house venting.  

RE: wht is the purpose of holes in man hole covers

These days most of the manholes are completely sealed packed. We have generally circular manhole covers. And about the holes, the presence of holes make the air pass through them so that the pressure created by the gases generated from the sewage do not exceed.

Thanks Bimr for sharing a great stuff with all.  

John
http://www.minidiggerhire.ie/#/skip-hire-dublin/4547725214

 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources