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

"International Fuel Gas Code"

on AbeBooks

or eBay or

Amazon

(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.

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

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

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.

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.

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.

A. HERE IN VA I'M A MASTER GAS FITTER AND ALL I USE IS COPPER CAUSE HERE THE MOISTURE IN THE AIR CAUSES RUST TO FORM ON THE EXPOSED PIPE THREADS CAUSING LEAKS , AND I EVEN PRO PRESS THE FITTING. HAVEN'T HAD A LEAK YET AND ALL LINES HOLD 15 PSI FOR 24 HRS BEFORE BEING INSPECTED. REALLY IT ALL DEPENDS ON LOCAL CODE.

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.

A. I HAD A 1/4" COPPER GAS LINE FOR MY HEATER'S PILOT LIGHT THAT FAILED WITH A CRACK ALONG ITS LENGTH. THIS TUBE HAD NO SOLDER JOINTS, JUST COMPRESSION FITTINGS. MY PLUMBING CONTRACTOR SAID IT WAS DUE TO THE ODORANT ADDITIVE THAT IS PUT INTO THE NATURAL GAS. HE REPLACED IT WITH AN ALUMINUM TUBE.

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.

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.

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!

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.

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)." (copper.org)

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.

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.

! 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 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!

I'm not sure what you do for a living but using COPPER PIPE FOR NG DISTRIBUTION IS NOT ILLEGAL IN THE STATES! Period!

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

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

"CODES
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."

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 troika. 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 don't argue with your advice; the internet should be used only to help find documentation and to open minds to things. Trusting it is dangerous, and I think people are likely to be more cautious rather than less after viewing this thread..

But the REALITY is I recently bought a clothes dryer & a kitchen stove "with installation". The "installers" were burly -- important for handling appliances. But when I asked about the adaptors and flex connection gas lines they were putting in (using the channel lock they used as a hammer and for nuts & bolts -- their only tool) they were clueless, no idea whether yellow teflon tape or pipe dope belonged or didn't belong on the gas line adaptors they were installing.

Another time, they installed a long length of plastic water line tubing with a hairline split in it to the icemaker in the fridge, causing extensive water damage to the cabinets before the water leaked out from behind them days later. I learned to demand copper tubing, not plastic, for the icemaker in my next home regardless of code assuring me that plastic is okay. Codes aren't based solely on safety -- or we wouldn't have devastating fires from lightning striking CSST lines in attics of condos, and sweeping from one unit to the next. Like everywhere, lobbying plays a huge part in allowing things that are cheaper but not as good.

We don't become master plumbers from 10 minutes of reading ... it takes 8700 hours. But that 10 minutes might warn folks that merely being listed as acceptable on a code doesn't doesn't necessarily make something the robust solution they should choose :-)

Thanks, and Regards,

"2024 Uniform Plumbing Code"

on AbeBooks

or eBay or

Amazon

(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.

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.

Regards,

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.

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.

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.

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.

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 passing through it -- I've certainly seen copper water pipes accidentally cut with a saber saw or drilled into; I suppose a steel (black iron) pipe could be, but someone would really have to work at it :-)

Regards,

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

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.

Thanks 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 countless 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 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,

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.

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

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

!! 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.

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

Regards,

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.

A. 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.

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.

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; but then an industry quickly becomes built upon the new technique -- complete with its lobbyists & lawyers ... and soon even fire marshalls are apparently intimidated to silence.

https://www.nbcdfw.com/investigations/Experts-Say-Flexible-Gas-Line-Lightning-Related-Fires-Continue-in-Spite-of-New-Safety-Measures-246966451.html

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

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - 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.

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.

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.
HOWEVER: COPPER IS COMPLETELY ACCEPTABLE IF COMPRESSION FITTINGS ARE USED. IN TEMPORARY SITUATIONS RUBBER, FLEX LINES ARE ALSO ACCEPTABLE.

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