C-900 vs. Ductile Iron

[ChrisPeterson]

Hello-
I work at a campus facility with significant amount of underground water mains ranging from 4" up to 16". Due to aging concerns, we are looking at replacing existing Cast and Ductile iron mains. It was recommended to use PVC/ AWWA-900 grade piping. Since I do not profess to be an expert, I was wondering where I can find some objective opinions/ expert advice on Pros and Cons of C-900 vs. ductile iron or other alternative. Any experienced advice would be greatly appreciated. My thoughts:
* total installed cost
* failure rates
* expected life
* Special considerations for installation/ operation/ maintenance.

Thank you!
- Chris Peterson

 

[EdStainless]

The first place to look is to see if papers have been presented at AWWA conferences.
And to see if they have printed any guides for the usage.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[CarlB]

An Eng-Tips thread:

https://www.eng-tips.com/viewthread.cfm?qid=365559

A water main break study:

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1173&context=mae_facpub

 

[JedClampett]

My advice is, if you're not planning on self-performing this design, ask some of the horizontal project design firms or contractors for their input. For a lead on a future project, these guys will be more than happy to have a phone call with you.
If you are planning on self-performing, you have a moral dilemma.

 

[ChrisPeterson]

Thank you for your feedback and links.

 

[bimr]

Look at this comparison:

comparison

 

[fel3]

bimr…

That's an interesting article. I was struck by that fact that steel pipe was only mentioned twice, both time in off-handed remarks.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[bimr]

fel3,

Nobody uses steel pipe where I have lived because of the corrosion issue. I believe some parts of the country where the conditions are more favorable i.e. dryer climate, steel may be an alternative.

 

[fel3]

Bimr…

Here in California I have designed quite a few miles worth of cement mortar lined and coated steel pipe for water and reclaimed water service and more than a mile of tape wrapped steel pipe for natural gas service. I have also used cement mortar lined and epoxy coated or painted steel pipe quite a few times for pumping station and well discharge piping. Sometimes the buried pipe was also encased on polyethylene tubes (just like DIP) and on one project we installed cathodic test stations, but no actual cathodic protection. In each case, I could have used ductile iron and either one would have fared about the same with respect to corrosion. I have used 6"-12" DIP for pumping station and well discharge piping, but in the larger sizes, DIP is generally not competitive here. This is because, IIRC, the nearest DIP manufacturer to California is in Texas, while I can get steel pipe right here. Thus, for me, transportation adds much more to the cost of DIP than it does to steel.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[hydrae]

I use C-900 all the time
A few vulnerabilities

Shading is important if using native backfill, but that is true of all buried pipes.

Inserting the spigot into the bell the correct distance and not all the way. If the pipe is consistently pushed to home,
the pipe can fracture starting where the spigot end touches the bell flare, the failure is a lengthwise split
requiring replacement of the whole length. The fracture can start 20 years later, (in winter, in the snow, on new years day)

Bending the pipe around corners. while allowed per spec, do not tap the pipe in these bends, again the failure mode is a lengthwise split.

Hydrae