Thread: Galvinized gas piping

I thought you didn't want black gas piping and galvanized used on a gas line together, but after calling this out on two inspections recently, both plumbers said that was just fine. Basically, a small section (8" pipe on the first house was galvanized, and 8' on the second) of galvanized was on a run where the rest was black pipe. My reporting language was something like, "It is not recommended to install dissimilar metals w/o proper connectors and galvanized pipe may shed material inside the pipe and clog gas valves.". That wasn't exactly it, but something to that affect. What gives with the plumbers? Maybe our Natural Gas up here in AK doesn't have a high enough sulfur content to make a difference?

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They are right.

Why though? When I do a search on this thread, that's what inspectors have said in the past, not to use them together.

H.I. folk lore has a life all it's own is why you keep hearing it but not seeing any documentation, requirements, or ills because it is used.
The real reason not to use galvanized is that it is more expensive and just not needed.
Will I get my panties in a twist because they threw in some galvanized fittings or nipples? Certainly not.
They are NOT dissimilar metals and the coating does not flake off any worse than rust in a steel pipe.
Debris in the line is taken care of by the sediment trap.
If anyone has any bona fide documentation to the contrary, I'm all ears.

Sorry for the long paste, this is from a past thread, HG Watson, Sr quote:

"Just because both materials are covered with the same ASTM standard (A53) doesn't mean they are the same final product or will behave the same, they certainly don't have the same surface films, or necessarily by grade or that they were manufactured by the same process, (ERW, FbW, etc.), or that they will be the same on the galvanic scale, or that galvanic corrosion is the only factor to consider (other corrosion processes especially as the zinc coating is "sacraficed" to the acids in the environment and the now uncoated & exposed steel starts to corrode - i.e. rust, as we see in Charlie's picture). Independantly they might be permitted in some jurisdictions to be used indoors customer side for a residence (with exceptions to higher air/moisture environments, exposed in laundry areas (due to exposure to acidic environments & moisture), etc., but IMO the materials should not be mixed. Personally, am not a fan of using sch. 40 or 80 galv for customer side of the meter once indoors for residential NG piping, especially intermittantly.

Other factors influencing the rate and extent of corrosion potential also depend on electrical resistance of the joint between the metals (the pipe dope or tape sealant, which is normally applied to the threads further tends to increase the joint's electrical resistance further decreasing the corrosion potential), conductivity of the electrolyte, relative areas or masses of the anodic metal vs. the cathodic metal, the polarization of the anodic metal through the buildup of adherent surface films.

Sulfur/sour gas should not use galvy.

The zinc coating will sacrifice (more active or anodic) to the steel ;its coating deteriorated the galvanized steel pipe will corrode (rust), transfering its corrosion process to the lacquered black steel pipe, a.k.a. "black iron pipe". NG pipes are not oxygen free environments, nor are they "water free". NG in the pipeline is regularly mixed with "air" to adjust down when the mix is "too rich". Condensation in the "lines" is common. Exposed, the OD is subject to oxygen, moisture (especially moisture enriched indoor conditioned occupied spaces).

Black steel pipe (black iron pipe) has a lacquer coating IIRC from oil when the steel is hot. Similar to the "seasoning" coating one strives for/desires on "black iron" cookware (steel) [by heating cycles with oil or fat coatings develops a protective and naturally non-stick coating which appears black and improves over time/usage and functions until damaged by detergents, salts, soaking or cooking acid foods, scraping, or lack of use, etc. and then must be "re-seasoned"].

Steel "likes" slightly alkaline environment (negatively charged as it is) and will not corrode in pressence of fluid that is slightly alkaline unless oxygen is present or when dissimilar metals are connected with the carbon steel. Expose Steel to acid environment (positive charge) and water/oxygen and it will corrode much more rapidly."

The rest of the thread didn't come to a concesus on the matter, but there is no code that disallows it I guess.

Sorry if this is covered in the copy of HG's post but I don't have time to read through it....

Some of the gas piping rules have to so with identification... as in, not confusing it with water piping and grounding a panel to it (of course bonding is now required but it didn't use to be). I always have to look this one up when I encounter it but I believe there's something about marking piping that is in an area without the appliance.

I've always figured the intent was if a furnace is in a room with copper gas piping to it somebody has a good chance of noticing it as opposed to a copper pipe just running through an area that you can't see what it goes to.

There's good concise info in the Code Check books... PM me if you can't find it and I'll look it up sometime. I'm too tired to go upstairs now

Okay.... one of the babies cried so I grabbed the book while upstairs....

It's required to be labeled every 5 feet if it's not black pipe and if it's in a room that doesn't have the equipment.

Here's the picture of the Code Check book.

Thanks Matt,
I appreciate your efforts! The thread cleared it up for me and I won't be mentioning it in a report unless the 5' requirement is not met.

I was quoted out of context.

Not only was my post snipped and therefore incomplete, it was specific to the materials photographed by the OP of the ORIGNAL topic string to which I posted.

NOT ALL "black pipe" is the same - Cast-Iron is NOT ALLOWED.

Next, they ARE disimilar (galvy vs. which ever black pipe) materials. Not only is the zinc coating of issue - so is the "recipe" of the steel/iron.

Third, lets make THIS complete here, regarding Standards for steel and wrought-iron pipes for gas (not limit to what was pictured in the thread topic my snipped post quoted out of context was taken from):


(quoting from Chapter 5 of NFPA 54, 2009 edition):

5.6.2.2 Steel and Wrought Iron. Steel and wrought-iron pipe shall be at least of standard weight (Scheule 40) and shall comply with one of the following standards:

(1) ANSI/ASME B36.10, Welded and Seamless Wrought Steel Pipe;
(2) ASTM A 53, Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated Welded and Seamless;
(3) ASTM A 106, Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service.

If you go back to my actual post which was snipped from another thread you will further see a list I posted of anodic to cathodic properties of metals. You might further notice the OP on THAT topic post string's photograph of deteriorating galvy (rusting, and zinc sacrificed) intermixed with non-galvinized materials.

NFPA 54 2009 edition (National Fuel Gas Code, aka NFGC aka ANSI Standard Z...) is currently freely available to preview on-line in read-only mode at NFPA you will have to register on the site with a valid email address and confirm it, and log-in to do so.

Also keep in mind in addition to your AHJ and local code adoptions, your NG utility may further restrict what materials are acceptable to be used to inter-connect to their supply system. The appliances being served and other components used within the gas system. Also keep in mind u/g cathodic protection systems and low voltage AC or DC current allowed to be on the metallic gas pipe from appliance and control (fail-safe) systems.

Finally, you can have some significant differing conditions than the "norm" most of us in the lower 48 deal with (esp. those down south "flatlands" in far less seismic or climatic extreme zones). For example, sustained low temperatures, some areas RAW gas supplies, altitude, deep freeze zones/heaving, seismic activity protections, deteriorating agents, etc. which effect specalized instructions and installations for both appliances and materials depending on circumstances (such as air-mixing systems etc.). You would be best served to first and foremost inquire of your local jurisdicational authority of what your codes/rules are, and the source of gas, local specialized language, conditions, etc. For example I assumed this was utility supplied "refined" (stripped of high btu and desireable gasses) NG, but realize might very well be RAW gas directly from a local well, or pipeline, or compressed or liquified gas supply. IIRC your extreme climate requires regulators indoors in conditioned spaces and then venting them outdoors, etc. Conditions we for the most part would be completely unfamiliar with.

Originally Posted by Matt Fellman

Okay.... one of the babies cried so I grabbed the book while upstairs....

It's required to be labeled every 5 feet if it's not black pipe and if it's in a room that doesn't have the equipment.

Here's the picture of the Code Check book.

Good info! I am trying to find the 5' marking rule in a code book and so far have had no luck. I see a 2412.5 code reference in your picture. Do they say what code they are referencing? (fuel gas, plumbing, mechanical) and what year? Thanks!

Originally Posted by James Duffin

Good info! I am trying to find the 5' marking rule in a code book and so far have had no luck. I see a 2412.5 code reference in your picture. Do they say what code they are referencing? (fuel gas, plumbing, mechanical) and what year? Thanks!

I found it in my Code Check Complete book. Plumbing section, sub-set Gas Piping, 96. I has a footnote to it which states;

The 2006 IRC rule simplifies the the req for labeling gas pipe to apply to all but steel -- the 2003 rule is for all but black pipe.