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!

*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.

Jobs

HDPE/PVC for Water Main Replacement within Bridge

HDPE/PVC for Water Main Replacement within Bridge

(OP)
I have a steel main that crosses 400' span bridge. The water main resides within a below-grade cell and supported at 10' intervals. The water main has experienced significant corrosion at the existing bell & spigot joints and will need to be replaced.

One potential option is to replace the pipe with either HDPE or PVC. Since it will reside in a below-grade cell, there will be minimal UV exposure. What are your opinions with this material selection?

RE: HDPE/PVC for Water Main Replacement within Bridge

You may need to add intermediate supports.

I found conflicting information about whether PVC is suitable for water service.
The gray DWV stuff i have worked with has a distinct odor, and I'd expect a taste.

Mike Halloran
Pembroke Pines, FL, USA

RE: HDPE/PVC for Water Main Replacement within Bridge

oahu93

Either could work but HDPE would be better. PVC is suitable for water service but is probably better buried.
HDPE has the advantage that you can weld it all into one long length and install it whereas PVC would probably have to be installed length by length.If you pull all 400 foot of HDPE in at once that would allow you to join it out on the bank somewhere, pressure test it then pull it in.

Depending upon the size and wall thickness etc you may have to support at closer than 10 foot intervals but this will apply equally to PVC or HDPE. For reference see the comments below and the attached file from the Poly pipe Engineering Guide

SAG
The amount of sag in mid-span depends upon the weight of the pipe per foot, including effluent. Figure J-1 gives
the recommended spacing for a mid-span deflection of one-quarter of an inch when full of water. However, in
situations where a dry gas is being carried, the indicated span can be doubled. When condensation occurs in the
pipeline, the liquid accumulates in the sag, unless the pipe is sloped; therefore, accelerating the sag due to the
increased weight. If less deflection is desired, new support spacing can be determined by multiplying the spacing
by the following correction factors:
1. 0.67 for 0.05 inch (1.3 mm) deflection
2. 0.80 for 0.10 inch (2.5 mm) deflection
3. 0.88 for 0.15 inch (3.8 mm) deflection
4. 0.95 for 0.20 inch (5.1 mm) deflection


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: HDPE/PVC for Water Main Replacement within Bridge

hdpe and pvc will expand and contract with temperature change. not the best application for plastic pipe. maybe FRP would be better. if you use steel, than provide cathodic protectioin and bond all the joints

RE: HDPE/PVC for Water Main Replacement within Bridge

Ductile iron?

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

RE: HDPE/PVC for Water Main Replacement within Bridge

Quote (mike)

I found conflicting information about whether PVC is suitable for water service.
The gray DWV stuff i have worked with has a distinct odor, and I'd expect a taste.

PVC is commonly used for water, see AWWA C900 and C905
gray DWV is intend for Drainage, Waste and Vents, and is not intended for potable water.

RE: HDPE/PVC for Water Main Replacement within Bridge

Expansion and contraction with temperature change is a problem with any pipe system and must be catered for. However HDPE would be able to be used in this application okay with a few requirements. I have attached one of the relevant sections of the Poly Pipe Engineering Guide.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: HDPE/PVC for Water Main Replacement within Bridge

I would use cement lined ductile iron for this application based on the little information provided, restrain all the joints, and provide expansion couplings at either end.

Mike,
PVC has been used for decades for potable water and in the several areas I've practiced is the default material for potable water, sewage force mains, and gravity sewage lines.
Can you post a link or links to articles which have found PVC unsuitable for potable water?

RE: HDPE/PVC for Water Main Replacement within Bridge

jgailla

I don't have a link but in the past some of the concern has been around lead levels in some of the pipes but i think it was discovered that this primarily related to sewer and drainage grades.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: HDPE/PVC for Water Main Replacement within Bridge

Agree with cvg, this is not a good application for HDPE or PVC. The expansion of FRP with temperature will be much less and equivalent to steel. Steel or ductile iron are also good alternatives.

Consider the use of a higher quality coating system.

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


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close