Galvanized lining for potable steel water pipe?

[sportsnut44]

Is it a good idea or bad idea to galvanize both the inside and outside of potable steel water pipe (2-inch size)? I know the galvanizing will over time taint the taste, but I heard the amount of chemical that leaches out into the water is not dangerous. True? Are there any health departments you know of that do not allow this? Would the piping suffer early corrosion if it was not internally lined by galvanizing?

 

[micalbrch]

Stainless steel is better than galvanized steel but is more expensive - you know that. Galvanized steel is o.k. for cold potable water but over a few years not for warm potable water. I know that galvanized pipes must not be bendend and that welding seam corrosion is an issue with galvanized pipes. That's why they are usually connected by fittings.

About health danger: Zinc is a heavy metal. That does not have to mean anything but it does not sound good for me.

 

[orenda1168]

Further to micalbrch's post, and for your consideration, the EPA Secondary Potable Water Standard for zinc is 5 mg/L. This is a non-enforceable standard.

Orenda

 

[bimr]

Galvanized piping is always galvanized on both the interior and exterior. The entire pipe is dipped into a galvanizing solution.

Galvanized piping is commonly used for building services. The extent that piping corrosion occurs depends to a large measure on the characteristics of the water.

For the most part, galvanized piping is in common use and it would be rare if enough material leached off of a pipe to create a hazard.

 

[rconner]

It may be helpful and/or protective of your Customers to check to see that your prospective manufacturer has appropriate certification or qualification (e.g. per NSF 61 standard), that their products are suitable for contact with potable water (and perhaps even tested etc. at the range of temperatures expected for the application).

 

[sportsnut44]

Thank you all for the feedback. I found out that in 1986, the first galvanized pipe manufacturer was certified to ANSI/NSF Standard 61 for its hop dip galvanized pipe for potable use. Since then, galvanizers have had their material and processes evaluated in accordance with ANSI/NSF-61 with great success. However, it is incumbent upon the purchaser to determine if the supplier has the appropriate approvals to demonstrate acceptability in domestic water systems. There is a common misconception that galvanized lined pipe taints and even poisons drinking water when used for transporting potable water. It is true that some minerals and chemical properties of drinking water will dissolve the zinc coating on steel pipes; however, they are in such small quantities as not to harm the human body. In my particular case, a 2" galvanized steel pipe was chosen for cold water service out to the end of a pier for it's strength and durability in that application.

I want to clarify something that was said above, i.e. that galvanized pipe is ALWAYS inside and out. That is not true. We are seeing pipe from China that is capped at each end before it's dipped so only the exterior receives the galvanizing. So, in our case the contractor was trying to use pipe that was not galvanized on the inside (even though required) and likely from a facility that is not certified to NSF Standard 61. I point this out as a caution to others that galvanized pipe does not always mean both inside and out.

Thanks again for the input.

 

[rconner]

Seeing some additional information provided here, and I guess regardless what material is considered, one other thing may bear mentioning.

While I guess all of us with any degree of experience understand the difficulties of building anything with 100% control and compliance with every law, rule and regulations out there (when we must after all in the end, “Git er’ done!), and cheap prices are also a powerful incentive to many, it is my understanding per status a couple years ago (e.g. see site at

http://www.nsf.org/business/water_distribution/pdf/ASDWA_Survey.pdf

) that,

“NSF/ANSI Standard 61: 46 states and 11 provinces/territories have legislation, regulations or policies requiring or recommending drinking water system components to comply with NSF/ANSI Standard 61.”

At some point one would almost have to think that some degree of enforcement might follow, at least to try to assure some level of reasonably substantial compliance (and to minimize risks to the Consumer).


“There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.” John Ruskin 1819-1900

 

[bimr]

Additional clarifications are in order.

ANSI/NSF-61 establishes minimum health effects requirements for the chemical contaminants and impurities that are indirectly imparted to drinking water from products, components, and materials used in drinking water systems. This Standard does not establish performance, taste and odor, or microbial growth support requirements for drinking water system products, components, or materials.

Galvanized pipe must be specified to meet the ASTM A53 pipe performance standard:

http://www.astm.org/Standards/A53.htm

The ASTM A53 standard requires pipe to be hot dipped galvanized. At the present time, galvanized pipe for potable water applications is ALWAYS required to be galvanized on both the interior and the exterior.

Galvanized pipe and tube is produced by two methods; one is semi-continuous where stock lengths of tube are cleaned and passed continuously through a bath of molten zinc at 450 degrees centigrade.

The other method is continuous where strip is formed into tube from coil and the tube then passed through a bath of molten zinc at 450 degrees centigrade. This second method coats the exterior of the tube only.

Coating characteristics: The semi-continuously applied coating is a conventional galvanized coating having a coating thickness typically around 65 microns which consists largely of zinc-iron alloy layers as the free zinc layer is largely removed through air wiping during the process. The continuous tube galvanizing process produces a bright coating which is almost all free zinc with very thin alloy layers, giving the product good forming properties. Coating thickness is typically 12-25 microns on the exterior of the tube only.

General or hot dip galvanizing involves preparing work by acid pickling in batches or on jigs and then dipping the work into a bath of molten zinc.

Coating characteristics: The typical general galvanized coating ranges from 65 microns to over 300 microns depending on the steel analysis, thickness of material and immersion time in the galvanizing bath. Typical coating thickness on most general galvanized products is 80-100 microns.

The exterior coated galvanized pipe is not used for potable water applications.

http://www.idodsystems.com/galprocess.html

http://www.galvanizeit.org/images/uploads/publicationPDFs/Z-ZC-06.pdf

Finally, this is not a good application for galvanized pipe. Your best choice for piping materials in marine applications is not galvanized pipe but a non-metallic piping system such as FRP. The joints on galvanized piping are susceptible to corrosion when the pipes are threaded. FRP has many of the properties of metallic piping, without the corrosion and can be interchanged with the metallic piping.

http://www.ameron-fpg.com/files/pdf/FP707A.pdf

http://www.compositesworld.com/articles/offshore-applications-the-future-is-now

http://www.ameron-fpg.com/files/pdf/FP845A.pdf

 

[rconner]

While it is true that fiberglass material has some utility, and particularly perhaps even most in some marine applications, as to the part of the comment, “FRP has many of the properties of metallic piping", I think all would at least agree they are both sorta long, and at some point have at least one hole in each end ;>) (While I guess it has been around since ~WWII, per EPA et al it does not yet have widespread use in e.g. municipal water piping in the USA -- news I saw just yesterday at

http://234next.com/csp/cms/sites/Next/News/National/5568483-147/story.csp

is some indication that even into this 21st century there could perhaps be reasons beyond the good looks and pleasing personalities of alternative material folks why this is the case).

 

[sportsnut44]

Putting FRP, PVC or HDPE under a pier subject to extreme high tides and likely contact with floating debris at times would not be wise in my opinion. Ductile iron and/or steel is needed for it's durability to withstand abuse in this type of environment, as long as it's properly protected against corrosion.

 

[bimr]

sportsnut44, if you have any question regarding durability of FRP, please refer to the following article that describes wrapping of marine piles with FRP:

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA508938

http://rebar.ecn.purdue.edu/ect/links/technologies/civil/cp40.aspx

http://www.mms.gov/tarprojects/392/392.pdf

"No material or combination of materials has the answer to all the problems faced in the rugged offshore/marine environment, says McDermott’s Landry — there are advantages and limitations to all groups. “Disadvantages of FRP are impact resistance, initial cost of material vs. carbon steel and some reluctance on the part of regulatory agencies. On the other hand, composites offer corrosion resistance, light weight, ease of installation, no maintenance and long service life.”

http://www.compositesworld.com/articles/composite-pipe-valves-offer-corrosion-free-performance

 

[bimr]

rconner

The article lacks details of the installation (ie. pipe material, construction method, pressure, etc.), and smacks of a typical municipal cheap political trick.

 

[rconner]

I went back and re-read the article, and while admittedly all the information you talk about is not provided it does say what kind of pipe was/is involved in the recent construction it refers to that reportedly went awry (and it appears “smacking” someone both in terms of unintended extra cost and completion), and also what kind of pipe was to be used in the replacement of same. While I guess you could well have more experience than I in the local area, or maybe even this work, is it possible the originally chosen pipe was (sort of like it sounds,“cheap”/inadequate for whatever the/all local conditions were) and/or any “trickery” may have been instead on the part of some who said it was? While there are always excuses for anything that goes wrong (and admittedly no pipe is perfect), in the long run I guess some people don’t like things going wrong or having to pay extra, non-budgeted money for even brand new construction.

 

[bimr]

Agreed that no one likes to pay extra for the specified standard construction.

However, the article does not state what material (pressure rating) was specified, whether the specification was adequate for the intended use, whether the furnished material met the specification, whether the material was installed correctly, why the material was failed, yada yada yada.

In summary, it is difficult to develop a technical discussion off of a newspaper article written by a non-technical person.