Underground Stainless Steel Water Pipeline and Tank Rehab

I am refurbishing a 50 year old, partially buried, wire wound concrete potable water tank in the DFW, TX area. I would like to replace all the existing cast iron tank piping and undergroung piping with welded 304 Sch. 10 stainless steel piping. Please let me know if you have had success with underground SS water piping or not, especially with tank refurbishments. Tank nozzles have cast iron sleeves and must remain. Any concerns with galvanic corrosion? Any suggestions on tank refurbishment based on experience will be appreciated too, especially successful (or non-successful) AWWA approved tank coatings. Your help will be appreciated.

 

[KernOily]

Why did you select 304SS? Will it be directly buried, or will it have an exterior coating? Does SS meet the UPC and/or your local plumbing/building code requirements? Why not use plastic (PVC/CPVC/HDPE)?

I'd also think you will need to pay close attnetion to your soil characteristics to ensure you do not get a chloride stress cracking problem, especially at the butt welds. Thanks!
Pete

 

I am currently in the pipe selection process. A concrete - wire wound - tank manufacturer recommended not using PVC pipe because expansion / contraction would cause tank connections to leak. He recommended cast or ductile iron, however, our existing cast iron piping has lots of rust tubercles. I would like to try a better material with less potential for rusting. Several of my contacts have recommended 304 SS. I just found one project in Big Rapids, MI where a bottled water manufacturer installed a 12 mile long, twin, 8" dia., wrapped, 304 stainless steel pipeline. The lines were orbital welded and acid passivated. They are happy with the results.

I am going to research this further. I am especially concerned about galvanic corrosion (CI sleeves vs. SS pipe) and chloride stress cracking corrosion. SS should meet AWWA code--it is used for food and beverage piping--but I need to verify this.

 

[mcguire]

There is abundant successful experience with buried 304. The standard precautions apply and you seem aware of them.
The cast iron will be corroded more rapidly because of the galvanic couple and the rust from it could harm the stainless. Use 304L if welds can't be quickly cooled.
I discount the risk of SCC in this environment,ie ambient temperatures and low risk of pitting to initiate the SCC.
Why don't you get some field experience from one of the large pipe producers from whom you might buy the pipe to supplement what you get from eng-tips?

 

Thanks for the recommendation on 304L. I'll look into it. I may also try to place a dielectric between the SS & CI (and/or some sacrificial anodes). I did follow your advice on the producers (and installers) and found some more useful advice. Extruded plastic coated pipe was used on the MI springwater project. For the sake of long pipe life and potable water protection, I think I will propose it for this project.

 

You can't be serious? This is for potable water right? Specify DICL (double cement lined ductile iron pipe). This is the standard in the water industry. There is no need as a professional engineer to be placing the cost burdon of SS pipe onto your client for this application.

Sorry to sound so critical, but there is no need to reinvent the wheel on water engineering, believe me!!!

PS: I would not place welded joint pipe into tank influent/effluent pipe applications.

 

I'll look into the DICL. Thanks for recommending it as an option.

Please explain further why you would not use welded joint pipe for the tank influent/effluent.

 

[11echo]

I'm surprised nobody has "mentioned" the COST of S.STL. piping! I would suggest "plastic" piping systems, PVC, CPVC, or (ideally) HDPE. So long as temperatures are not above 200 deg. F. Also, expansion of piping would not be a factor in buried piping systems. These "plastic" piping components will save you money on both material cost and construction cost, way above the S.Stl. application. "Galvanic action" would not be a concern here. The only other consideration would be UV erosion if you “daylight” this piping, but they even have plastic material to deal with that too. Good Luck! ...Mark