PVC vs HDPE

[dzyn]

We have designed a water distribution system to be PVC. The system supplies both domestic and fire service to 20+ warehouses. After the contract award the gov't PM and the contractor want to know if HDPE pipe may be used in stead.
Can the two be used interchangably? I've seen some literature where HDPE has be used to replace old DI lines. There is also some debate about whether the chemicals in water systems degrade the HDPE lines over time more quickly than PVC. I'm looking for information on installation procedures also. Can the two be placed at the same depth below vehicular loading and using the same bedding materials. What have your experiences been in the field?

 

[RWF7437]

http://plasticpipe.org/index.html

 

[Artisi]

Can you use "plastic" pipe on fire service?

 

[dzyn]

Our fire protection engineer told me the requirement is for DI to the 5' line outside the building, in this case it is existing; we are replacing all the mains and service lines outside the 5' line.

 

[LUDPEKA1]

Can you be more specific when you say “PVC”.

 

[Sterilecuckoo58]

I have little experience with PE pipe for pressure. My recollection (so I go back 12 years) was that you butt weld the pe pipe as you install it and mobilizing the welder is big $ so push on PVC is more cost effective. (Also, I know how to install push on pvc, but welding PE for a pressure application? I am necessarily dubious becasue I can't do it.) I'd sooner apply a compression fitting which I think are available for smaller diameters.

Corrugated pe can be buried with as little as 1-foot of cover (flexible pavement or gravel but not under rigid pavement) but your bedding material and compaction has to be A-1, otherwise you're toast. Remember, before fiinal grading you won't even have that 1-ft of cover.

I flunked chemistry twice (okay, it was O.Chem.) before I passed it but I would investigate the particular water chemistry in the supply system and check compatibility for PE and PVC on checmical resistance charts.

 

[semo]

HDPE pipe is commonly used for waterlines. As mentioned, it must be fused together instead of push joints; but, as such, it can be made into a long length that can be directional bored under pavements, ditches, etc.

There are several things to take into account with HDPE pipe:

Make sure you look at the sizing of the pipe as the HDPE has a thicker wall; therefore, you might need to upsize the pipe to obtain the same interior diameter.

You also need to spell out what SDR class you want as various SDR classes have various pressure ratings as well.

Also the coefficient of thermal expansion is different than other materials and depending on the method of installation(ie boring, opencut,etc.), restraints may be needed at the connections to prevent the pipe from pulling away from the connections.

You are doing right by investigating the differences.

A search on HDPE waterline will yield you plenty of info. Another good source of info is AWWA's publication "PE Pipe - Design and Installation".

 

[11echo]

I've dealt with both types of "plastic" pipe, I think you'll find PVC is easier to install if it’s an above ground installation & on supports. HDPE requires special tooling and a degree of proficiency with these tools to do it correctly. Also you need to know that certain type of HDPE (orange colored) does not stand up to the sun's U.V., how ever the black colored does. HDPE is like a wet noodle, so installation on the ground or buried is where it starts to be the material of choice. Temperature considerations also need to be addressed, HDPE can and does deal with cold weather very well, PVC not so much. These are some of the issues I'm aware of regarding these materials. Good Luck!

 

[dicksewerrat]

The project manager and the contractor? want to change things after bid award? Ask them what the trade off for HDPE will be? Has the fire marshall signed off on the HDPE?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com