Gas Pipe Materials


From the 2015 International Fuel Gas Code (IFGC)


  • Cast iron: Not ALLOWED
  • Steel: Black iron or galvanized. Schedule 40 minimum.
    • ASTM B36.10 or 10M
    • ASTM A53/A53M
    • ASTMA106
  • Copper or copper alloy: Check with the local Gas Utility. Permissible use varies with hydrogen sulfide (H2S) content of gas. Excessive levels of H2S reacts chemically with copper to produce particles that can become lodged in the gas valve if no sediment trap is installed. Most natural gas is OK.
  • Aluminum-alloy: Seldom used due to highly reactive characteristics.
    • ASTM B241 (must be marked at both pipe ends indicating compliance).
    • Alloy 5456 prohibited


  • Steel tubing: Typically used only in industrial applications and for appliances
    • ASTM A254
  • Copper tubing or copper-alloy tubing:
    • ASTM B280
    • Standard types K and L, not M.
  • Aluminum tubing:
    • ASTM B210 or B241
    • Must have a protective coating applied where it contacts masonry, plaster, or insulation, or where it may be repeatedly wetted by water, detergent, or sewage.
    • May not be used underground or at exterior locations.


Plastic tubing is allowed outside and underground only.

  • Polyethylene (PE)
    • Must be marked “GAS” and “ASTM 2513”
  • PEX: PEX is short for “cross-linked polyethylene”. It’s simply polyethylene with polymers added to enhance certain characteristics. Requirements are the same as for polyethylene.
  • Polyamide
    • ASTM F2785 (may be different in the past)
  • Polyvinyl Chloride (PVC): NOT ALLOWED
  • Chlorinated Polyvinyl Chloride (CPVC): NOT ALLOWED

Difference Between Pipe and Tube

  • Diameter
    • Pipe is measured by inside diameter
    • Tube is measured by outside diameter
  • Wall thickness
    • Pipe is described by “schedule thickness” (schedule 20, 40, etc.)
    • Tube is described by “gauge” for thinner tube, and by fractions of an inch or millimeter for thicker tubing.
  • Cross-sectional shape:
    • Pipe is always round
    • Tube may be round or square.
  • Manufacturing tolerances
    • Tube is typically manufactured to closer tolerances than pipe

I still have to add CSST.


Thanks for the share Kenton

Well done! I’ve struggled for years at a national laboratory as a Pipe Fitter explaining the difference between pipe and tube to “Engineers”. The problem often was drawings call out for pipe, specs were for tube category.


1 Like

Ooooop! Thank you Simon!

Nice reference. I think the description of tube/pipe diameter are reversed. Tubing is measured by the outside diameter, pipe on the inside.

You’re right, Michael. I had to check 5 websites and they averaged out to what you said. The first one (the one I first used) was a manufacturer’s website. You’d think that this is something they’d agree on!

The home had corrugated stainless steel tubing (CSST) installed as gas distribution pipe. CSST is a thin-walled, semi-rigid, corrugated stainless steel tubing covered by a jacket that is typically yellow, sometimes black. Safety concerns exist concerning the ability of CSST to resist potential damage from lightning strikes- or near strikes- resulting in gas leakage and risk of explosion.
CSST has been the subject of a lawsuit that has now been settled. Pipes named in the suit are marked with one of the following: GASTITE,WARDFLEX, TRACPIPE, COUNTERSTRIKE or PARFLEX. Gas pipes in this home consisted of CSST which contained one or more of these markings. Installations of concern are those pipes installed after September 5, 2006.
Installed correctly, CSST must be properly bonded and grounded. Inspection of CSST requires the inspector to have a copy of American National Standards Institute (ANSI) LC-1/CSA6.26 plus a copy of the manufacturer’s installation instructions. For this reason, inspection of CSST lies beyond the scope of the General Home Inspection. The Inspector recommends that inspection of the CSST gas piping be performed by a qualified plumbing contractor.

CSST buried but not listed
The home had corrugated stainless steel tubing (CSST) installed as gas distribution pipe. Although the Inspector disclaims full inspection of the CSST, the Inspector observed portions of CSST pipe directly buried underground. CSST must be listed for direct burial. The Inspector was unable to see any markings on the CSST indicating that it was listed for this application. This condition is potentially hazardous and the Inspector recommends full inspection by a qualified plumbing contractor.

CSST not bonded
The home had corrugated stainless steel tubing (CSST) installed as gas pipe that was not electrically bonded. CSST has specific bonding requirements that must be complied with for safety reasons. The Inspector recommends correction by a qualified contractor.

CSST improperly bonded
The home had corrugated stainless steel tubing (CSST) installed that was not properly bonded. CSST has specific bonding requirements that must be complied with for safety reasons. The Inspector recommends correction by a qualified contractor.


  1. All pipe is to be made of a long hole, surrounded by metal or plastic, centered around the hole.

  2. All pipe is to be hollow throughout the entire length – do not use holes of different length than the pipe.

  3. The I.D. (inside diameter) of all pipe must not exceed the O.D. (outside diameter) – otherwise the hole will be on the outside of said pipe.

  4. All pipe is to be supplied with nothing in the hole, so that water, steam or other stuff can be put inside at a later date.

  5. All pipe should be supplied without rust – This can be more readily applied at the job site. Some vendors are now able to supply pre-rusted pipe. If available in your area, this product is recommended as it will save a lot of time on the job site.

  6. All pipe over 500 feet (153m) in length should have the words “long pipe” clearly painted on each end, so the Contractor will know it is a long pipe.

  7. Pipe over 2 miles (3.2 km) in length must have the words “very long pipe” painted in the middle, so the Contractor will not have to walk the entire length of the pipe to determine whether or not it is a long pipe, or a very long pipe.

  8. All pipe over 6” (152 mm) in diameter must have the words “large pipe” painted on it, so the Contractor will not mistake it for a small pipe.

  9. Flanges must be used on all pipe. Flanges must have holes for bolts quite separate from the big hole in the middle.

  10. When ordering 90 degrees, 45 degrees or 30 degrees elbow, be sure to specify right hand or left hand; otherwise you will end up going the wrong way.

  11. Be sure to specify to your vendor whether you want level, uphill, or downhill pipe. If you use downhill pipe for going uphill, the water will flow the wrong way.

  12. All couplings should have either right hand or left hand thread, but do not mix the threads - otherwise, as the coupling is being screwed on one pipe, it is unscrewed from the other.


Now that sounds like something I would say however, I would say it is not necessary for a home inspector to check the bonding. Why? Because all CSST is bonded.

Unless they are doing a code inspection.

That make’s perfect sense, a plumbing Contractor recommendation is the only way to go!

I never trusted it!
That last time, I insisted they break out pipe and threader!

Also if you read;

They also recommend ; it’s smart to have your piping system inspected by a licensed electrician.

CSST pipes may not have been installed to current model code requirements

Some 500,000 new homes in the United States have CSST installed each year. But since regulations directing how pipes are bonded and grounded were not adopted until 2006, it’s smart to have your piping system inspected by a licensed electrician.

Properly bonding and grounding a CSST gas line system is critical

Direct bonding better secures electrical continuity and conductivity through metal pipes, while grounding can send any lightning strike into the ground. CSST systems installed before the bonding/grounding rules are susceptible to lightning strikes, which can cause electrical shocks.

Direct bonding on your natural gas system reduces the chances of electrical shock, as well as a natural gas leak or fire.

CSST pipes can be damaged by lightning

Lightning striking a CSST gas line system can be extremely dangerous. A strike on or near a building can travel through the structure’s piping system and cause a damaging power surge that can produce a gas leak or fire.

This is gene a-s-s LOL

Now, that is funny. I don’t care who you are. :joy: :rofl:

LOL! Good one, Martin!