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Best pipe for natural gas lines: Copper vs. steel, plastic, CSST, etc.

Internet postings can be used a guide to where to find sources for authoritative answers, but the advice should not be trusted directly. This thread is a great example of experienced specialists & professionals expressing widely differing advice, opinions, and even understandings :-)

Q. I recently bought a home and almost immediately had a terrible gas leak. It turned out that the gas pipes for part of the heating system is copper and had corroded. I understand that copper pipes for carrying natural gas is not up to code in California. However it appears that copper pipes for gas were allowed at some point in time. Can anyone tell me how long ago Copper was considered OK for gas pipes. Also how long does it take for gas to corrode copper?

Seema Nanda
- Los Angeles, California

"International Fuel Gas Code"

on AbeBooks

or eBay or


(affil links)

A. Natural gas does not [itself actually] corrode anything, including copper. Corrosion is a chemical reaction between metal and oxygen. It is the oxygen in the normal air that is mixed in with the gas that would cause any corrosion. The corrosion may also be accelerated by heat and moisture. Is it possible that humidity or water got into the pipe? I don't have the info on gas pipe specifications, sorry! I do highly recommend that you use whatever material is current California code. Natural gas leaks are not something you want to mess around with.

tim neveau
Tim Neveau
Rochester Hills, Michigan

A. As you know, the makeup of a natural gas piping system also contains a foul smell to identify any leaks in a system.
This generally contains a small amount of methyl mercaptan.
This chemical contains and will react with the copper to form copper sulfide which will eventually corrode through the pipe

Mark Frister
General Contractor - Milwaukie
February 9, 2022

A. No. Odorants do not contain methyl mercaptan. Methyl mercaptan is toxic. Odorants are mixtures of other sulfur compounds. Those compounds aren't corrosive to copper and are at very low (e.g. parts per million) concentration.

The sulfur compound that corrodes copper is hydrogen sulfide (H2S), also a toxic gas. H2S is removed before gas is put into the pipeline system because it also corrodes the steel pipe used to transport natural gas from production to end user.

That said, if the local fuel codes don't allow copper don't use copper.

John Erickson, PE
- St Pete Beach Florida
November 5, 2022

A. Natural gas has sulfur, that is the main reason it's not suitable for CH4 [methane].

Anthony Monah
- Connecticut
November 6, 2023

A. I was a gas service representative for a few years and was instructed that natural gas in copper pipe over some period of years caused copper sulfites which clogged up the pipe with hard, black crystallization. Reps regularly recommended customers switch to galvanized pipes when feasible and steel flex hose connections to gas shut off valves.

Mary Lou Bonilla
- Fresno, California

A. I am employed in the plumbing industry, and most Natural Gas piping is installed by plumbing contractors. It is my understanding that gas has no effect on the copper pipe itself; the problem is the way the pipe is joined. When the pipe is joined with plain old solder that is used for water piping, it will flake off and build up causing problems. When installed correctly, using silver solder, flared joint and mechanical press joining, copper can be the most economic way to install gas pipe.

William J. Stanton
- Waukesha, Wisconsin

thumbs up sign My father was a master plumber and plumbing contractor, and is probably rolling over in his grave :-)

I have no qualifications in the subject myself, just my recollections of him fuming every time he saw copper pipe :-)

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

A. LOL, hello guys I'm a licensed pipefitter/plumber/gas technician , personally I've never seen a copper pipe being corroded by the gas itself. Corrosion is usually the cause of what's in the oxygen we breathe, and/or the mixture of different metallic fittings -- and to use copper tubing with just regular solder is totally forbidden here in Canada, only silver solder is permitted. And a service man must be pretty lazy to use copper tubing unless it was in an extremely confined space where steel pipe can't be fitted.

- Sherbrooke, Quebec, Canada

Ed. note: Welcome! Feel free to visit anonymously! But our 35-year legacy of warm aloha is incompatible with anonymity; please only post with your full real name.


- VA BEACH Virginia USA
November 10, 2022

Q. I have a remote camp in Maine, which is off-grid, and where I use LP for lighting, refrigeration, and kitchen range, and may expand to other uses as well. With the recent rise in the price of copper, our region has experienced increased theft of copper, and many camps have been raided for their copper tubing. My question is: What alternatives to copper tubing are there that are homeowner-friendly (do it yourself), and that will remove the temptation of thieves from ripping out my gas lines?

Brian Athorp
- Dedham, Maine

A. The only thing I see in my area is natural gas rather than LP, Brian, but black iron pipe is all I ever see in my homes and the homes of family and friends. I suspect it's okay for LP, but I'm sure that there are codes you should check. Good luck.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Q. The gas line to my water heater is a copper tubing. A plumber told me that the additive put in natural gas corrodes the copper from the inside out. Since I don't know about copper, I had no reason not to believe him. I am wanting to know if this is true or not.

Gloria P

Gloria Plank
consumer - Pearland, Texas


- CONCORD, California

A. As an applications engineer in the metals industry, I know a little bit about corrosion. Enough to be dangerous, anyway.

Natural gas on its own may not have a huge corrosive impact on copper. And copper is typically not corroded by oxygen due to its noble nature. What will corrode copper rapidly is oxidizing or reducing sulfur environments. Sulfur is added to natural gas to give off the rotten egg smell to warn us of leaks (without it, natural gas is actually odorless). This sulfur is probably what attacked your copper line.

The above is only my guess.

Alex Mak
- Vancouver, BC, Canada

A. Copper is ok, flare fittings are best.
Test with liquid soap or gauge.
Black steel is best indoors but no one wants to work anymore so they have this new stuff called track pipe.

Anthony Schiavone
- rye brook New York

A. Been installing water heaters for many years now. TRUST ME, BLACK IRON PIPE or GALVANIZED ONLY for ANY gas line! That's it that's all! I could write pages and pages of why you shouldn't use anything but those two materials, but won't. If you want safety first, follow my years of experienced advice!

Kevin West
- Sunnyvale, California
January 30, 2009

A. Copper pipe, or tubing is NEVER ALLOWED BY CODE IN THE US FOR NATURAL GAS DISTRIBUTION! There are various reasons for this which I'm not going to even bother getting into because they are irrelevant. Bottom line is copper is NEVER ALLOWED BY CODE IN THE US FOR NATURAL GAS DISTRIBUTION!
It is very common to see copper tubing used in rural areas for propane gas distribution. This is allowed. Propane and natural gas are two different gasses.
Steel pipe is allowed in residential and commercial construction inside of buildings. There is direct burial plastic tubing types allowed outdoors, underground. They must come out of the ground via a steel riser.
If you don't want to use rigid black steel or rigid galvanized steel, and go through the trouble of cutting and threading, there are different brands of flexible, stainless steel, plastic sheathed tubing (Ward-Flex is an example) that can be used, but this requires a license or permit to purchase in most areas.
Also, CAST IRON fittings may NOT be used either for propane or natural gas. They are for steam fitting and DWV (drain, waste or vent) installations. Malleable iron only!

If you have copper in your building used for natural gas, I strongly suggest replacing it ASAP!

Also, if you live in an area where propane was used, and the public utility has extended their service area to include your home, before converting to NG, I would advise checking your system first to make sure a previous contractor has not plumbed your gas with copper. It will need to be changed.

Scott McManus
- Binghamton, New York
June 27, 2009

A. This quote answers the question:
"Copper and copper alloy tube (except tin-lined copper tube) should not be used if the gas contains more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet (scf) of gas (0.7 mg/100 L)." (

For the most part the chemical added to make the gas smell is what corrodes the copper and not the natural gas itself. If your local gas supplier has reduced the additive to this amount or substituted sulfides for something else you would be ok. But for safety I'd suggest using black pipe for supply and coated flexline or flexible aluminium line for compression fittings.

Daniel Nonya
- Philadelphia, Pennsylvania
November 17, 2009

A. I do not know the US Code, but the Code for natural gas in Canada is as follows...

"Natural Gas can be run with

-Copper tubing DESIGNATED and rated for natural gas by use of flare fittings only

-Black iron pipe schedule 40 or thicker with only black malleable fittings (NO GALVANIZED PIPE OR FITTINGS ALLOWED)

-Polyethylene pipe for underground installations only

-Corrugated Stainless Steel Tubing CSST

-Steel tubing DESIGNATED and rated for natural gas by use of flare fittings only"

Remember, the copper tube allowed in Canada must be the type rated for Natural Gas, regular retail stores do not carry this type of tubing, only HVAC suppliers have it.

Ronvall Lentin
- Hamilton, Ontario, Canada
December 17, 2009

! I'm a plumber (for twenty years). We install gas lines, but I don't know it all. Worse than not knowing it all, there is a lot of myth and hearsay among plumbers--especially Canadian plumbers--just kidding, co-worker is a chatty Northerner. Anyway, I've always heard that copper is not allowed for gas distribution but I couldn't really remember why except for a faint recollection of it having something to do with an additive. It's in the plumbing code. You can get away with it in some places but why try.

Unless you're like me and on a Sunday you decide to adjust the location of your pilot on your wall furnace because the "the plumber" before you put it too far from the fire box hanging loosely in the air only supported by the ALUMINUM gas supply tube (ha! got you guys! no one has mentioned aluminum yet have they!) to which the furnace pilot is attached. So I grabbed it, move it, and it snapped (I'm more of a big pipe, new construction type of plumber guy). So I'll use copper for a few days until I find a place that sells 1/4" aluminum tube that's open when I get off from work. I wasn't sure how long I could get away with it.

Thanks for the info everyone!

Robert Bustamante
- Los Angeles, California
January 24, 2010

thumbs down sign I'm not sure what you do for a living but you shouldn't be giving advice on a topic that you so clearly have no business! Using COPPER PIPE FOR NG DISTRIBUTION IS NOT ILLEGAL IN THE STATES! Period!

Cal Contractor
- sulfur, Louisiana
November 5, 2023

Ed. note: Welcome! Feel free to visit anonymously! But our 35-year legacy of warm aloha is incompatible with anonymity; please only post with your full real name.
This posting is a good illustration of why: people posting with their real name rarely speak rudely & dismissively; people posting anonymously often do so :-(

Q. I am a Property Inspector and I remember reading about dissimilar metal connections in plumbing. I can't seem to find materials on the impact this has on gas pipes but if the copper pipes are in contact with sheet metal that is used in ducting, particularly if it is galvanized sheet metal, does anyone feel that this would cause a galvanic reaction which would cause it to corrode over time and eventually leak.

I am very concerned about this and would like some opinions from gas fitters.

Mark Johnstone
- Vancouver BC Canada
March 14, 2010

Q. Does propane damage copper pipe like natural gas? A boat surveyor said that propane damages copper pipe over time, however I don't see any sign of deterioration.


Dave Shively
boater - Aurora, Oregon
March 18, 2010

Ed. note: Scott M claims in his entry, that copper is widely used for propane, and your boat is another example. Thread/topic 5892 claims the same.

Q. I have an older boiler that the pilot would not stay lit this year. Upon closer inspection I found the aluminum tubing had corroded in just one spot. It was touching the metal frame on the floor. I found it when I lit the pilot and two other flames started nearby. After removing it most of the aluminum is in good condition except where it touched the frame. Is this normal or what?

Dan Mates
- Kalamazoo, Michigan

A. For a less anecdotal and more engineering oriented response to the question go to COPPER.ORG and search 'natural gas'.

Ernie Ruda
- Atlanta Georgia
October 18, 2010

"Basic plumbing"
by Howard C. Massey

on AbeBooks

or eBay or


(affil links)

thumbs up signHi, Ernie. Can you please point us to a specific article or articles on that trade group's site? I followed your instruction but was presented with a list of 754 articles, the first few of which seemed to offer no sense of balance at all -- which is probably to be expected from a trade group whose mission is to promote the use of copper. I agree that engineering oriented responses trump anecdotes, but to my mind you get one-sided promotional literature from trade groups :-)


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

A. The following excerpt is from, search 'natural gas", Fuel Gas Distribution Design Guide:

Based on tests carried out by the Gas Research Institute, and with more than 35 years of successful use of copper by certain gas companies in the United States, major code bodies in the USA and Canada have approved copper tube for fuel gas systems. In 1989 in the USA, provisions for the use of copper tube and copper alloy fittings for interior distribution systems were incorporated in the National Fuel Gas Code (ANSI Z223.1 / NFPA 54). Similar provision is made in the Canadian document CAN/CGA-B149.1 (CGSB 41.22 [withdrawn]), Natural Gas Installation Code. Since then, there has been an increasing demand for information on this application. The National Fuel Gas Code also provides for the use of copper tube and copper alloy fittings for underground service lines from the main to the meter."

Kevin Kiefer
- Marietta, Georgia, USA

Ed. note: Thank you Kevin!

! I am shocked at all of you. To trust the safety of your lives and those surrounding you to the internet! I have seen way too many "He said he knew how to do it"! In reading the answers above if I were a laymen I would be more confused. Call a PROFESSIONAL ... Codes change, what was deemed ok in the 60's is so far out of date.. example (flex lines were made from brass, aluminum etc., but are no longer used). Codes change due to research and well D-I-Y Boo Boo's and etc.
Please call a professional in your area for advice and codes in your country or state or county or OMG city.

Tom Smith
appliance service - Kingman, Arizona
July 21, 2011

Hi, Tom.

My father was a master plumber and I remember as a child the endless evening hours he spent practicing lead wiping and other skills for the hands-on examinations by the board. It's easier these days, but even today to become a master plumber in our area requires 700 hours of classroom time plus 8000 hours of OJT. Yes, master plumbers are professionals -- you certainly don't have to sell me on that!

And I certainly can't argue with your advice in the abstract; the internet should be used only to help find authoritative documents and to open minds to things that should be considered. Trusting internet information is dangerous; someone could claim to be a licensed professional, while actually being a hacker up to no good. When sections of codes are quoted here, I hope that people don't trust those citations, but use them to find those sections, not as a substitute for looking at the code themselves. And having seen such a range of divergent thoughts on this thread, I think people are likely to be more cautious rather than less cautious.

But the REALITY of the situation is that I recently bought a gas clothes dryer and a gas kitchen stove, both "with installation". The "installers" in both instances were big & strong -- an important qualification for handling appliances. But when I asked them about the adaptors and flex connection gas lines they were putting in (using the same channel locks they used as hammers and for nuts and bolts, the only tool in their possession) they were clueless. They didn't have the vaguest idea whether yellow teflon tape or pipe dope belonged or didn't belong on the gas line work they were doing.

On another occasion, for a refrigerator, they installed a long length of plastic water line tubing with a hairline split in it to the icemaker, causing a lot of water damage by the time the water leaked out from behind the cabinets. Thus there is value in homeowner having a feel for what is right and wrong. Codes are not based solely on safety -- like everything else, lobbying plays a big part in allowing things that are cheaper but not as good. I learned to demand copper tubing, not plastic, for the icemaker in my next home regardless of the code assuring me that plastic is fine.

We won't become master plumbers from 10 minutes of reading ... it takes 8700 hours. But it just might help spot shoddy or dangerous work by an unqualified installer -- which seems to be almost all of them when one buys an appliance these days :-)

Thanks, and Regards,

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

"2024 Uniform Plumbing Code"

on AbeBooks

or eBay or


(affil links)

A. Copper pipe, type L or K is allowed under the Uniform Plumbing Code ⇨
Section 1209.5.2.3. Copper and brass pipe may be used if the gas contains no more that an average of 0.3 grains of hydrogen sulfide per 100 scf of gas (0.7 mg/100L).

We use it in Seattle because our gas doesn't have that much HS. Your town might. You'd better be sure. Lots of places are now allowing plastic PE pipe. The gas company here now sets all of its new lines in plastic. Professionals can buy plastic PE pipe for light commercial and residential projects. Many rules surround how it can be installed though. Not something I would recommend for a DIY'er.

PJ Lewan
- Seattle, Washington, USA

Q. I got to this thread in an attempt to find out why the flared copper tubing to my water heater is so pitted and why it is so full of black crystals that look like sand. It is unfortunate that there are posts made by people who would recommend using materials that I now know to be dangerous.

My water heater and my furnace are the two gas appliances in my house. The gas meter is right on the other side of the outside wall to my water heater. Iron pipe runs from the meter for a few feet through the outside wall, then about two feet of flared copper tubing goes to the water heater.

After replacing the water heater, I looked at the pipe and was shocked at the extent of the pitting on both flares and on the inside of the pipe. The pitting is remarkable in the amount of surface area and its depth. I don't know when my water heater was installed, but a sticker has an ANSI number that ends with "-1987". I presume, then, that the copper pipe was installed in the late 1980s; it is now 2011 as I post this.

copper flare corroded by natrual gas

One picture shows one end of the flared copper tubing that went to my water heater. Notice that the pitting not only covers much of the flare surface and almost reaches the outside, but also completely covers the inside of the pipe. The second picture is of *some* of the "sand" that was at the gas inlet of the water heater. I use the word "some" because there was a LOT more in the adapter and because the water tank had been dragged to my back yard, laid on its side, and rolled around a bit; I don't know if there was more than this, but just covering only half of the screen would seem to be an issue to my layperson eyes.

The place that sold me the water heater said that copper is against code (at least where I live); I replaced it with yellow coated stainless steel flex line.

This thread made me glad that I didn't call a "professional" to install the water heater - someone who might have said, "trust me I've been doing this for forty years and copper cannot corrode."

Bob Owen
- Texarkana, Texas, USA
August 11, 2011

Readers: Is it possible that Bob's "black crystals / black sand" is activated carbon that is supposed to be there, held in place by the screen? Because that's what it looks like to me, but I wouldn't know whether gas appliances ever have activated carbon at the gas inlet for some reason.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Q. Ted - there was much more of the black stuff on the flare side of the adapter. I simply blew compressed air through that and the copper line before realizing just how serious the problem was (no longer anything to photograph). It is uneven in consistency and doesn't look like something that was intended to be on either side of the adapter.

Bob Owen [returning]
- Texarkana, Texas USA

Q. I recently purchased a house, and upon moving in noticed the smell of natural gas. After inspecting the appliances I noticed that the compression fitting on the water heater was damaged and the previous owner had wrapped electrical tape around it!! The damage must have occurred after my inspection. Anyway, it was an old 1/4" copper line that snaked about 15' under the block and beam house to a network of CPVC piping. All the connections had yellow glue and seemed to be in good condition. Am I sitting on a time bomb? I'm looking at a considerable investment to replace all the runs with iron. Recommendations?

Travis Bour
- Montgomery, Texas USA
September 12, 2011

A. Natural gas in some states has a high HYDROGEN SULFIDE content, and this is what corrodes and attacks the copper -- which is why it is probably illegal in California. The mercaptin additive for odor has nothing to do with it.

Ryan Scott
- Edgewood, New Mexico, USA

A. Methanethiol (methyl mercaptan) is added to natural gas and LP to give it a rotten cabbage odor. It has an odor threshold of as low as 0.002 ppm. Its sole purpose is to allow people to detect a gas leak. Methyl mercaptan will react with copper pipe to produce copper sulfide, a black colored powder. Aside from the slow corrosion seen with copper pipe the copper sulfide powder (flakes) can clog a pilot light orifice. I have seen many older homes with copper pipe used for gas. It is my understanding that it is against code for natural gas in most states. However, because the amount of methyl mercaptan is more controlled in LP than NG it is acceptable to use for LP. Personally, I would and have used for LP for outside lines but when it came into the house I switched to black iron pipe. In many older towns a wick in a jar of methyl mercaptan at points along the gas distribution system is used to introduce the mercaptan into the gas. There is very little control in how much mercaptan is in the natural gas. As a result the rate of copper pipe corrosion varies from system to system. To be on the safe side use black iron pipe for natural gas.

Tom Mayer
- Cartersville, Georgia, USA
February 8, 2012

thumbs up sign I read this whole thread with amusement. Here in the United Kingdom inside a property about the only sort of pipe that is used for natural gas is copper. If you have a really old property (which means generally means pre WWII), then you might have some iron pipe if it has not been refurbished/updated in the interim but that is very rare.

Now what might actually corrode copper pipe is any gypsum based products. Consequently any copper pipe that passes through a wall or plaster must be sleeved with plastic or a wrapped in a special tape regardless of whether it carries water or gas. You can even buy the pipe covered in plastic, and colour coded in yellow for gas and white for central heating.

I guess if there was a really high hydrogen sulfide content in the natural gas that might be a problem, though I would guess in California earthquakes are more likely to be the reason for steel pipes over copper. Regardless, the experience in the U.K. would indicate that copper pipe and natural gas are not a problem corrosion wise. Plastic pipes are never permitted for gas inside a property as a fire would rapidly lead to an uncontrolled gas escape.

On the other hand browsing the web would indicate that in general plumbing state side is very conservative. I saw an article about solder ring fittings for joining copper pipes from the mid 2000's and people worrying about how they would last; we have been using then in the U.K. for over 50 years.

Jonathan Buzzard
- Dundee, United Kingdom

thumbs down sign I can't believe the things I have read on this post. Iron pipe is worse than copper as it requires a gasketing material to seal. I am a very highly qualified gas heating and plumbing engineer and have always used copper over iron unless there is a chance of vandalism or in case of emergency escape route for structural reasons, in which case normal preference is to weld steel. I have qualifications in air con, oil, lpg, ng, plumbing, disinfection, air source, ground source, rain water harvesting. Countries vary but the UK is very strict on regs as how many unvented tanks have blown up in the UK as opposed to America/Spain.

chris spencer
- cleckheaton, yorkshire, england
May 10, 2012

thumbs up sign Thanks, Jonathan. Thanks, Chris.

The constituents in natural gas as supplied by the utility may be different in the UK than in the USA. Or homes may be constructed differently. This thread does not prove that copper is "better" or iron is "better", but I have found it quite illuminating.

The important thing is to comply with the local codes. Sometimes we don't know what thoughts were in the heads of the code-writers. After reading this whole thread I still wonder whether code-writers might be concerned about hidden gas leaks being caused by people using an electric saber saw or drill on a plasterboard wall with a copper gas pipe concealed within it -- I've certainly seen copper water pipes accidentally cut with a saber saw in that situation; I suppose a steel (black iron) pipe could be, but someone would have to work quite hard at it :-)


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

A. PG&E serves Northern & Central California. Copper service lines were installed in the 1940s and 1950s. A replacement program was completed in 2014 due to internal corrosion leaks and internal deposits which would block off flow. In the 1970s, PG&E servicemen were directed to replace all copper flexible appliance connectors encountered, due to safety issues.

Don't install it, and take out what you have.

Sr. Gas Transmission & Distribution Pipeline Engineer, PE

Drew Kelly
- San Jose, California, USA
March 1, 2015

Q. Thanks Drew! What are flex connectors made of? -- they seem to be the only thing offered out here (although they have a yellow plastic covering on them and I don't know if they are made of stainless steel as Bob O suggests, or something else).


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

A. Very Interesting Internet Conversation on Copper vs. Steel Pipe. As A Licensed Technician In Ontario Canada I am Familiar with the National and Local Codes and use all 3 materials depending on the job requirements. I carry Black Iron, Steel Pipe and Gas Copper in my Installation Vehicle.
In Canada and the USA the National Gas code Permits all 3 materials to be used: Gas Copper, Black Iron, Steel Pipe and CSST. All 3 must be installed by a licensed Gas Technician holding Certification in all 3 Materials. The Job Requirement, Piping Access, and in some cases Visual Appearance, determine the installation. In all cases the piping should be installed by a Licensed Technician.
From the Internet comments here, it appears that there are a lot of D-I-Ys giving advice that is Incorrect or Blatantly false or "Their Opinion". These are the facts here in Canada. Thank you for your time.

Martin Harrison
- Toronto Ontario Canada
October 25, 2015

thumbs up signThanks Martin. It's true that you see "opinion" here, but Seema's question has been on line for 13 years and has been viewed by hundreds or thousands of qualified plumbers, pipefitters, and gas technicians -- and many have responded with conflicting opinions.

Seema says copper pipe was installed, presumably by licensed technicians, was presumably inspected by the proper authorities, and yet failed. Seema believes that copper was in accord with earlier code, but not 2002 code -- yet per your posting it is perhaps still okay. So is it okay, and was it ever okay? If so, why did it corrode and how long might it have taken? Is there any direction she should take? Is copper gas piping to a water heater advisable despite the several problems reported here? ... some things that are legal are not advisable based on frequency of problems, etc.

My own experience as a member of several professional organizations & trade associations leads me to believe that the movement away from black iron pipe, toward copper and plastic, was far more likely a result of pressure from trade groups and an effort to reduce costs rather than a response to any safety problems with black iron pipe. After a decade and a half of postings, I don't think anyone has suggested a safety problem with black iron pipe (just that the labor cost is high).

Please correct me if I'm reading it wrong, but while safety findings occasionally cause code changes, cost cutting and pressure from trade groups seem to be the driving force far more often -- as witness the many explosions and fires from lightning strikes to CSST gas lines in attic spaces -- yet they are still allowed and being run :-(
Why? Because it's cheap. In such cases I don't care what the code allows, you're not putting a CSST gas line in my attic.

Regards and thanks again,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

thumbs up sign I found this thread per chance on Google and enjoyed reading it. In my experience I have personally changed quite a few copper gas lines to black iron piping during the late 1990's. The copper tubing was clearly pitted throughout its length and the wall thickness was noticeably thinner. I do not know from what chemical, I would guess sulfur compounds after reading this thread. LP is fine for copper tubing. Even to this day I see welded schedule 40 pipe for 3" and above and threaded black iron for 2 1/2" and below on all natural gas lines.

John Richter
HVAC, TAB and Cx - Lancaster, Pennsylvania usa
November 9, 2016


April 25, 2016

Q. It appears to be coming known in the UK that 'black powder' is responsible for the failure of Worcester Bosch domestic boilers. They recommend replacement of the copper gas supply pipe from the meter ... with new copper pipe! But does the powder come from the iron mains supply? We only have about a metre of pipe between the meter and boiler, and it is only seven years old. GJ

Graham Johnson
- Southampton, UK
January 24, 2017

A. Shah,
Perhaps one could prime and paint the joints to protect from the environment.

Can you order black steel pipe instead? That is the material used in my area.

blake kneedler
Blake Kneedler
Feather Hollow Eng. - Stockton, California
February 5, 2017

!! We bought an older home (1954), and got a new dryer. Company REFUSED to hook up due to copper tubing (like the kind used for a swamp cooler). I crawled under and repiped with black steel. The old copper was SO brittle it broke apart as I removed it. Thank God they didn't install! It was a disaster just waiting to happen.

Alan Weinel
- Galt, California USA
November 29, 2016

Q. Following up my previous question, I have had an analysis of the black powder.

copper - 550,000 mg/kg
sulfur - 106,000 mg/kg
iron - 6,790 mg/kg

Other elements were detected in much smaller quantities. It seems that the use of mercaptans for smell leads to clogged filters and boiler shutdown in the UK.

Graham Johnson [returning]
- Southampton, England, UK

fuel gas and copper pipe

! Those with an interest in this thread might find this article also interesting .

It basically acknowledges that an issue exists; but brushes it off (IMO) based on future sulfur content of the gas (installer must predict the future accurately); and a 20 year service lifetime.

I live in a house that is over 50 years old; my father's house is well over 100 years old. Having to re-plumb every 20 years strikes me as absurd.

And the recent disaster in Flint, Michigan, USA shows how difficult it is to predict the future when it comes to public utilities like gas or water. Don't forget, the water they were putting into the pipes was safe, the lead poisoning came from lead that the water leached out of the pipes! The lead pipes worked fine for 50 years or more; until someone changed the content of the water being run through them. There is nothing that prevents that from happening with natural gas, either.

The above referenced article even acknowledges that 21,000 properties in Great Britain have been affected by supplying high sulfur natural gas from the North Sea.

Randolf Younger
retired - Los Angeles, California, USA
June 9, 2017

thumbs up sign  Thanks Randolf, excellent points! claims that steel is 34% more expensive ... but it sounds to me like it's worth it.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

A. Late to the game here but I'm a licensed gasfitter in MN doing mostly residential work and have never seen that kind of pitting on copper pipe. I run into just about as many copper gas lines as black iron. Both are allowed by code here. Just to echo some of the others, the percentage of additives seems to be higher in some areas than others. And I'll reiterate as well: follow your local codes.

Luke Johnson
- Eden Prairie, Minnesota USA
March 10, 2018

A. Ok here it is. I do this for a living in Texas. Copper can be used for ground lines although poly is better and cheaper. Copper can be used inside but black steel or galvanized is the norm. Copper cannot penetrate walls or concrete, it must be sleeved where it penetrates these areas. Steel nipples are usually used for these spots, but even steel nipples must be sleeved going through concrete. Must Have shutoff valves located within 4' of appliance with approved flex lines. All copper must have flared fittings or silver solder connections only.


CSST = Corrugated stainless steel tubing

Best bet use steel inside, copper or poly for outside ground lines. CSST can be used inside but not recommended due to all the lightning strikes popping holes in the lines during storms.
If it is used, I don't care what brand it is don't use it unless it's been properly grounded.

Rob Turner
Propane company - Pipe creek, Texas Usa

thumbs down sign I knew about flexible gas lines being used for appliances of course; but I had no idea (until I looked up CSST to better understand your posting) that houses are being built with corrugated tubing gas lines running through their attics.

The risks we take in the name of cost-cutting are horrifying; then an industry gets built upon the new technique, complete with its lobbyists & lawyers, and soon even fire marshalls are apparently intimidated to silence.

Yes, we have to obey the codes, but we don't have to be so foolish as to believe that such codes are based solely on safety -- they are mostly based on lobbying power :-(


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

A. If you're going to use CSST (Corrugated Stainless Steel) flex pipe for gas, you need to be sure to bond it to your home's electrical grounding system via (minimum) #6 copper (solid is best... the shorter with fewer twists and turns the better).

In the event of a lightning strike on or near the home, you need to dissipate that massive energy into the earth. If you don't, that energy can arc between materials, possibly causing pinholes, fire, explosions, etc. Bad stuff. The bonding clamp should go on either the first brass nut on the CSST - or right behind it on the black pipe right behind the transition. Be sure to clean the black pipe if you want to put it there, you need a good connection.

BTW - I'm in the "Twin tiers" of N. PA / S. NY) and the local natural gas companies (and LP dealers) have used soft copper (flared fittings) for years. Underground ... top of ground ... in buildings ... you name it. They no longer do this - but when I was coming up in the trades the "gas guy" (working for North Penn or NYSEG) would run soft copper right through the wall of the building if that's all he had on the truck. It was common local practice for decades. So it's not true that (paraphrasing) "copper is outlawed for gas distribution everywhere in the USA". Simply not true. When in doubt - check with your local code authority.

Joe Stoddard
Mountain Consulting Group - Corning, New York USA

thumbs up sign I am not a plumber, my only qualifications is a PhD in engineering & Physics and lots of DIY plumbing. I have used Cu pipe for Natural Gas with no problems in a decade. I have seen black iron pipe rust and leak, extremely dangerous. Even galvanized steel pipe is short lived in coastal and damp places.

Cu does last and in my view safer because it does not seem likely to fail catastrophically. Black iron pipe is just steel pipe painted black. Steel is short lived because it contains carbon for added strength, and carbon accelerates rust. The old time pure iron pipe lasted way longer but no one makes it. I suspect people are hanging on to steel pipe because it "USED" to last and maybe forgotten why. I doubt if it is as safe as other forms of gas piping but, I for sure cannot be certain, I have not done any scientific evaluation. Someone should.

John Davidson
Do it yourself-er - La Jolla, California
October 5, 2021

A. Hello.
My name is Gunny Skare, Retired Contractor.
I'm from Montana and California is very strict on codes. That's fine for them, in many circumstances copper works great. ALL the GAS fitters I have met here agree for here THREADED BLACK STEEL IS THE RECOMMENDED FOR MOST PERMANENT STRUCTURES.

Thanks for your input -- obviously you know your stuff.
Thanks again Gunny.

Gunny Skare
- C.F. Montana
February 19, 2023

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