×
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

Pipe Connection to Manhole

Pipe Connection to Manhole

Pipe Connection to Manhole

(OP)
We have a proposed situation where we have a 18" perforated pipe at a depth of 12' and then a 36" storm drain directly above it at a depth of 5'.  Due to proposed site conditions there is not a way to not have the pipes in this orientation.

Does anyone have ideas of how to connect these to a proposed 72" manhole?  The one way I am thinking is to use an inside drop structure for the 36" connection.

Thanks

 

RE: Pipe Connection to Manhole

Not really sure what your concerns are.

Outside drop manholes are typically preferred. A drop pipe is typically specified for a sewer entering a sanitary manhole at an elevation of 24 inches or more above the manhole invert. Some jurisdictions allow storm sewers to enter with higher drops.  

Inside drop connections are secured to the interior wall of the manhole and provide access for cleaning.

Due to the unequal earth pressures that would result from the backfilling operation in the vicinity of the manhole, the entire outside drop connection shall be encased in concrete.

Probably the best option is to use an outside drop for the 36-Inch and have the 36-Inch enter the manhole just above the 18-Inch.

In any case, you will have to have the approval of the local agency having jursidiction.

You will have to backfill with aggregrate. Due to the unequal earth pressures that would result from the backfilling operation in the vicinity of the manhole, the entire outside drop connection should be encased in concrete.

Here is a link to some examples:

http://old.lehi-ut.gov/userfiles/Sewer_Drain-SD.pdf

RE: Pipe Connection to Manhole

What is the perforated pipe draining? And Why? I'd expose the 36, take it out of service, then sink a manhole down to the 18. Doghouse the manhole as you get to the 18. Place a concrete slab under the manhole. Come back up to the 36, build a nappe curve and place a short MH section, top slab and MH ring and cover.  

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

RE: Pipe Connection to Manhole

Sounds like you are out of the range of a standard manhole.  Why not design a stormwater vault with an access hole.  If your standard manhole riser is 4 or 5 feet in diameter the 36 inch is too wide to make a typical connection to the riser.  Our standard is inside diameter of riser must be at least twice the outside diameter of the stormdrain pipe.

RE: Pipe Connection to Manhole

84 inch mh risers. Should be cheaper than reinforced concrete vault

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

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