DIP vs. HDPE? 2

[civilman72]

I work in the Rocky Mountains in Colorado. Every water district in my area requires the use of DIP for all water mains (generally 8" in size or larger). They will also allow the use of C900 for water mains. I have been asked by a client to propose the use of HDPE for the replacement of an existing 3" pvc plastic pipe. I know the District's first reaction will be "absolutely not!" These District's are not the most open-minded, mostly because I live in a small community and we do not have the most technically advanced people currently working for these Districts.

I guess my first question is: can anyone tell me why the use of DIP would be so important, especially when compared with HDPE? Please consider the following: I work in very cold conditions, lots of freeze/thaw, also bury these mains at least 8' deep, and the soil types can be very rocky.

I know the use of HDPE pipe is becoming more and more common for water mains, but I also believe it is fairly new in this type of use, so truly understanding it's life span seems to be an issue. From the little research I've done, it seems that the most important part of construction that ensures a longer life-span is correctly welding the joints together. Besides that, the installation seems fairly straight-forward.

Being the local PE that steps up the plate and attempts to educate the local municipalities to change their ways, is a long-standing challenge that I would prefer to not take. BUT, if I did, does anyone have a good reference source to start with?

Any advice or opinions would be appreciated.

 

[CivEnvEng98]

I could be wrong, but I thought there were no manufacturers that made DIP in anything under 4".

 

[ccor]

I ran into this same issue when I worked in Steamboat Springs. We were able to spec HDPE in some out-of-service-area developments (in-service-areas were required to have a minimum dia. of 6" for fire flow) and it has been working well with the longest in-place time of only about 5-years. Originally many problems were experienced when contractors would lay 1000-1500 ft of main on a hot day when the pipe was its longest, as temperature cooled the pipes would crack at the joints (or other weak points like taps and valves). The solution is to lay the pipe in a sort of serpentine fashion in the bottom of the straight trench. This of course causes problems with the inspector if they are working for the municipality and don't know that this is the correct thing to do.

Check out this website for some good information on all PE pipes though it probably doesn't have exactly what you are looking for. The Handbook is pretty valuable though:

http://www.plasticpipe.org/index01.php

I believe you can getPC350 DIP down to 3" though.

 

[rconner]

Despite the attempts to sell plastics on the perception of novelty or advancement, most types of contemporary pipes including hdpe have actually been around for many decades. It is highly unlikely in this day and age that "every water district" in your area (who must live with their systems) requires ductile iron pipe as a result of being close-minded or lacking "technical" advancement. While it is indeed true (per independent authorities) that it has been most difficult to confirm (in even the best environments, let alone in all kinds of weather and maintenance conditions suffered by many water authorities) for sure that hdpe joints or taps are properly fused, there are a great many other highly technical reasons why an Owner might prefer ductile iron pipe over hdpe pipe, and some of these reasons can be learned in the first two publications available for download at the website

http://www.dipra.org/

under the heading/web page, "Why Ductile Iron Pipe is Superior to Polyethylene Pipe".

 

[cvg]

I would think that basing the decision on whether to use iron pipe or polyethylene pipe upon a publication put out by the DIPRA is a little bit like letting the fox guard the hen house... I can't profess to know all the pros and cons, but I do know that the DIPRA has more to lose than the plastic pipe industry, thus the need to publish such documents as this one:

http://www.dipra.org/pdf/DIPvsHDPE.pdf

somebody please post something comparable for HDPE if available. I can provide the following site which has some useful information:

http://www.kwhpipe.ca/know_artwhite.asp

 

[JStephen]

I would suggest also that you confirm that there are local contractors willing and able to install this at a competitive price.

The problem that comes up is you can have a set of specs requiring a contractor to use something he's never used before, but lay the blame for any problems with the material on him. The pipe-contraction issue mentioned above is one example- that could have been some expensive knowledge to pick up.

In general, sales literature as mentioned above is useful, even if one-sided. If every utility around there uses DI, they probably know all the disadvantages of it. And if there aren't any, there wouldn't be much reason to switch other than installed cost.

 

[hydrae]

Many water utilities have been burned by the HDPE of the 60's and 70's, why just today, a water system I work with had a black poly break (actually last night at midnight)
And while the stuff in the system may not be the same quality at the product sold today, it is hard for systems to regain the trust in an product that should last 100 years or so when they have seen failures in 10 years.
At two years even the best spec's warrantee wear out.

Hydrae 2¢