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How long does it take for natural gas to corrode copper pipes?

An ongoing discussion from 2002 through 2015 . . .


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


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. 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

Uniform Plumbing Code


thumbsup2 My father was a licensed plumber then a plumbing contractor for his whole life. He is probably rolling over in his grave at the fact that his son would even let someone post a recommendation here that copper be used for natural gas :-)

I have no qualifications in the subject myself, just my recollection of him fuming the several times he saw it :-)

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
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.

Trex [last name deleted for privacy by Editor]
- Sherbrooke, Quebec, Canada


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 (do it yourself) friendly, that will remove the temptation of thieves from ripping out my gas lines?

Brian Athorp
- Dedham, Maine


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

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
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

February 11, 2008


- CONCORD, California

March 21, 2008

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

December 29, 2008

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

January 30, 2009

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

June 27, 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

November 17, 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

December 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

January 24, 2010

! 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

March 14, 2010

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 18, 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

Ed. note: Scott M claims in his entry of 6/27/09, that copper is widely used for propane, and your boat is another example. Letter 5892 claims the same.

October 18, 2010

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

October 25, 2010

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

Basic Plumbing

October 25, 2010

thumbsup2Hi, Ernie. Can you please point us to a specific article or articles on that trade-group's site? I followed your instruction and was presented with a list of 754 articles, the first few of which seemed to me 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 neutral & impartial anecdotes trump one-sided sales literature :-)


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

November 4, 2010

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, 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

July 21, 2011

! 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 DIY Boo Boo's and etc..
Please call a professional in your area for advise and codes in your country or state or county or OMG city.

Tom Smith
appliance service - Kingman, Arizona

July 21, 2011

Hi, Tom.

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 even claim to be a licensed professional, while actually being a hacker using a fictitious name and up to no good. When sections of codes are quoted here, I would hope that people use those citations to find those sections, not as a substitute for looking at the code themselves.

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

But the reality of the situation is that I recently bought a gas clothes dryer and a gas kitchen stove with "installation". The "installers" in both instances were big and strong -- an important qualification for such work. But when I questioned them about the adaptors and flex connection gas lines they were putting in (with the same channel locks they used as hammers and for nuts and bolts) they were clueless about what they were doing. 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. They also "installed" water line tubing with a hairline split in it to the icemaker on the fridge, causing a lot of water damage by the time the water leaked out from behind the cabinets. Thus there is value in a homeowner having some feel for what is right and wrong...

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

Thanks, and Regards,

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

August 9, 2011

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

August 11, 2011

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.


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 12, 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,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

August 12, 2011

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

September 12, 2011

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

February 8, 2012

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

February 29, 2012

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

April 7, 2012

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 sulphide 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

May 10, 2012

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

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 some code-writers might possibly have been concerned about hidden gas leaks being caused by people using an electric saber saw on a plasterboard wall with a copper gas pipe concealed within it :-)


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

March 1, 2015

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

February 2015

Q. Thanks Drew! What are flex connectors made of then -- 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,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

October 25, 2015

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 DIYs 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 2015

thumbsup2Thanks 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 still not advisable based on frequency of problems, etc.

My own experience as a member of professional organizations & trade associations leads me to believe that the movement away from black iron pipe, toward copper and plastic, was much more likely a result of pressure from trade groups to reduce costs rather than a response to a record of documented safety problems with black iron pipe. After all these postings, I don't think anyone has suggested any problem at all with black iron pipe except for the labor cost, but please correct me if I'm reading it wrong :-)

Regards and thanks again,

pic of Ted Mooney  
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

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