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topic 13277 p2

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

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A discussion started in 2002 but continuing through 2018

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.
Pine Beach, New Jersey
We need "Aloha" now more than ever

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 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

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.
Pine Beach, New Jersey
We need "Aloha" now more than ever

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.
Pine Beach, New Jersey
We need "Aloha" now more than ever

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

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 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 safety problems with black iron pipe. After a decade and a half of postings, I don't think anyone has ever suggested any problem whatsoever with black iron pipe (just that the labor cost is high), but please correct me if I'm reading it wrong :-)

Regards and thanks again,

pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
We need "Aloha" now more than ever

November 9, 2016

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 sulphur 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

April 25, 2016



February 5, 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

November 29, 2016

!! 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

January 24, 2017

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

April 3, 2017

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

copper - 550,000 mg/kg
sulphur - 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

June 9, 2017

! 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 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
Pine Beach, New Jersey
We need "Aloha" now more than ever

March 10, 2018

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

May 25, 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

June 2018

Thanks Rob. 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 were being built with corrugated tubing gas lines running through their attics.

thumbsdownThe risks we take in the name of cost-cutting are horrifying; then an industry gets built upon the new technique, complete with lobbyists & lawyers, and soon even fire marshalls are apparently intimidated to silence. "Wish I didn't know now what I didn't know then."


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
We need "Aloha" now more than ever

October 22, 2018

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

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