Carbon Steel in Potable Water System 1

[therealminger]

Hello,

Is it acceptable to use carbon steel pipe in a potable water system?

I am currently upgrading a fire protection system at a complex with approximately 5 buildings. There is one fire pump that services all the buildings and the pump was added a few years after the buildings were constructed. The water main was cut into and the fire pump was installed. The system is set up so water flows from the water main through the fire pump system, then back to the main and on to the complex. During normal operations all the treated water from the town source flows through the pump bypass. This means that all the fire water and potable water for the buildings run through the bypass. This bypass piping along with the rest of the fire system piping is made from carbon steel. The water main from the town is made of ductile iron.

I had contractor look at the fire pump regarding some upgrades to the system and he advised me that the carbon steel piping is not allowed by the National Plumbing Code of Canada. Is that correct? Should the existing carbon steel pipe be replaced? If so, what are acceptable materials?

Thank you

 

[bimr]

Most plumbing codes call for galvanized steel pipe, not carbon steel.

The application may dictate the need for steel piping to be lined and/ or coated with a plastic, tar, or rubber.

Building systems sometimes use carbon steel. However, it is very rare to have a water distribution made from carbon steel, because of the short lifetime due to corrosion.

 

[therealminger]

Thank you for the info.

Is corrosion the main reason that carbon steel is not used? Do you know if there are any health risks associated with drinking water from carbon steel pipes?

I have advised the employees not to drink the water until I can find out more information. The employees health is my main concern.

I would like to leave the carbon steel pipe in place, but if it is dangerous to the employees then I will replace it with lined pipe or something else deemed acceptable.

 

[rconner]

I am not familiar with all potentially applicable Canadian codes for dual systems inside and outside of buildings etc.; however, I have noticed a sort of history/overview of many different types of pipe used for potable water distribution, including decades of steel pipe use in the USA per Figure 1 on page 3 and Table 2 on page 5 of the U.S. Environmental Protection Agency document at

http://www.epa.gov/ogwdw/disinfection/tcr/pdfs/issuepaper_tcr_ds-inventory.pdf.

With regard to the latter question however regarding suitability for potable water/water quality, it appears that likely a great deal of unlined and galvanized steel pipe has been used for potable water service in the past and as noted in the aforementioned reference (and I suspect likely still used in many areas of the world, including the USA); however, see per Figure 1 of the aforementioned reference that after the 1950's there was more common promotion/use of cement mortar linings for at least the type of distribution piping included in this history. This is not by accident as cement mortar linings can at least in some aggressive water conditions be important to minimize internal corrosion and maintain flow properties over time.
Most states in the USA now require that all new materials/pipes/linings/coatings etc. in contact with potable water have ANSI/NSF 61 listing as suitable for that service. While perhaps you could check to see if your sort of piping had/has any similar/comparable listing, I guess the lack of a listing would of course not necessarily mean that there would be a problem with any sort of existing pipe. You might therefore want to at least check current ANSI/NSF 61 (or other applicable standards) pipe and lining vendor certification/lists for pipes that look like yours, with your local water provider for more information experience with such pipes and their specific water analyses, and/or actually have the water coming out of the taps tested. I guess some water might go bad in any pipe material after a given period of time, depending on what one does or doesn't do to it!
I think for many reasons, including the standard availability of suitable/proven cement mortar linings, buried piping for dual service (potable water and fire protection) in the USA in say the most commonly used sizes of 6” (~150mm) through 16” (~400mm) is more likely to be cement mortar lined ductile iron pipe than any sort of steel (see percentage entries in Table 2 etc.) On the other hand, there is some significant use of cement mortar lined steel pipe in some areas for very large diameter water transmission. I think AWWA Manual M11 for steel water pipes (depicting now 6”-144” sizes in some tables) now mentions various types of linings/coatings for steel pipe, and further says that “linings must meet toxicological requirements for potable water”. However, it also gives readers an additional statement that cement mortar linings “have provided many years of excellent service”.
I would think piping inside buildings, including perhaps some smaller sizes of plumbing etc., could conceivably involve some different considerations, experiences, and codes.

 

[JStephen]

Carbon steel is widely used in different water applications, although generally with various coatings. Not only piping, but pressure tanks and storage tanks. I'm not aware of any health risks associated with it. The composition isn't chemically that different from cast iron and ductile iron that have been used for all sorts of water piping. And of course, carbon steel is the main structural component even in concrete piping and tankage.

There are AWWA standards for carbon steel pipe, and linings and coatings for it.

 

[bimr]

Corrosion is the main reason that carbon steel is not used for drinking water applications. The useful life of the carbon steel piping depends on the water quality parameters.

There are no health risks associated with drinking water from carbon steel pipes.

 

[kenvlach]

Everyone who drinks water that's flowed through a steel pipe will die (eventually).

All steel materials refined since 1945 contain greater-than-natural radioactivity (as do all other materials and people). Low radioactivity steel can be salvaged from pre-1945 structures and ships; notably, from the German ships scuttled at Scapa Flow.

Actually, steel and its cast iron kin are among the safest healthwise of common piping & plumbing materials -- unlike lead-leaching bronze & old solders, or toxic-leaching plastics and epoxies. Perhaps only concrete (non-asbestos), glass (as in Pyrex, not the resin-contaminated FRP) and gold are safer.

The only reason steel isn't used for all piping is limited corrosion resistance. Thus, its use is greatly restricted by the National Plumbing Code of Canada. Your existing steel piping may be illegal if the buildings are non-industrial or if considered part of the water distribution system, although existing steel piping can perhaps remain if originally legal:

From a legal case:

'1.Sentence 7.2.6.7.(1) of the Building Code states that welded and seamless steel pipe shall not be used in a plumbing system, except as follows:
"Galvanized steel pipe may be used in a drainage system or a venting system above ground inside a building". (Sentence 7.2.6.7.(2))
AND:
"Galvanized steel pipe shall not be used in a water distribution system except:
a.in buildings of industrial occupancy, or
b.for the repair of existing galvanized steel piping systems". (Sentence 7.2.6.7.(3))

Article 1.1.3.2.     Definition of Words and Phrases
Water Distribution System means an assembly of pipes, fittings, valves and appurtenances that conveys water from the water service pipe or private water supply system to water supply outlets, fixtures, plumbing appliances and devices.
...
Commission Ruling:
In favour of the Applicant. It is the decision of the Building Code Commission that the water service pipe conforms to the requirements of the Building Code.
1.Reasons:
1.The pipe is installed before the water meter and is considered a water service pipe. It contains no branches and is not considered part of the water distribution system.
2.The water service pipe is 6" in diameter with a sufficiently slow flow not making it susceptible to restricted flow from corrosion.
3.The water service pipe is accessible across its entire length.
4.Evidence presented suggests that large diameter galvanized pipe has been used in other municipalities on the basis of past performance.
Dated at Toronto, this 20th day, in the month of June, in the year 1995..."'

http://www.obc.mah.gov.on.ca/userfiles/HTML/nts_4_9935_1.html

The same language is in the
National Plumbing Code of Canada 1995
First Revisions and Errata
August 1999
which gives a useful Table A-2.7 of materials usable by application. For galvanized steel pipe (footnote 9):
"(9) Permitted only in buildings of industrial occupancy as described in the National Building Code 1995, or the repair of existing galvanized steel piping systems."

http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc46015.pdf