I wrote to an engineer concerning the usage of copper tubing with natural
gas. I asked him why it wasn't allowed until the mid 80's and what change
took place that permitted its usage.
Listed is the kind reply from Andrew concerning Copper Tubing being used
with natural gas.
Your question was: In our newsgroup, Alt.HVAC we are discussing the use of
copper tubing being used for Natural gas. We know that it is allowed now,
but this was not allowed until the early 80's. Use on propane however was
Why wasn't copper permitted until then for natural gas but was permitted to
be used with propane?
What has changed since then?
Does copper or flake or not when exposed to Natural gas? I was always under
the impression that natural gas wasn't as purely refined to remove sulfur to
an acceptable level and probably the refining has improved, is this correct?
Thank you very much, and I hope you permit me to copy and paste your reply
on the newsgroup or you may visit the discussion and answer it there under
'gas and copper fittings'.
Thank you very much
Response: Dear Rich,
Sorry for the delay in answering your inquiry.
While copper wasn't included as a recognized material in the National Fuel
Gas Code until 1989, it was widely used for natural gas systems in various
areas of the country. Areas such as the state of Minnesota, Birmingham,
Alabama and surrounding areas, St. Lous, Missouri, and the Washington D.C.
area. Most of the areas have successfully used copper for natural gas
distribution for 40-plus years.
However, other areas of the country did not permit the use of copper in
natural gas systems. The main reason being a difference in the quality of
the natural gas being supplied. In those areas where copper was used
successfully, their natural gas streams were either naturally low in
hydrogen sulfide, or they processed their gas to remove hydrogen sulfide. In
areas where the levels of hydrogen sulfide were high, they didn't allow the
use of copper, or if they did use copper found that they would experience
black flaking caused by the reaction of the hydrogen sulfide with the copper
tube. In general, even in the worst systems reaction was not sufficient to
cause failure of the piping system, but the flakes could result in nuisance
service calls if they blocked burner orifices, valves etc. and resulted in a
As the natural gas industry has evolved, the treatment of gas streams to
remove hydrogen sulfide gas has steadily improved, and requirements to
control the level of hydrogen sulfide provided in gases either supplied to
or taken from interstate pipelines has resulted in a reduction of hydrogen
sulfide levels in most gas streams to levels that eliminate the flaking
concerns previously encountered in copper systems.
As you had stated, this was never a problem with LP gas systems because the
hydrogen sulfide levels in these "manufactured" gases were more tightly
As a result of the improvements in natural gas processing, the industry is
now able to take advantage of the many benefits that copper has been
offering for LP gas installations for many years.
I hope this answers your question and again I'm sorry for the delay. If you
would like more information please feel free to contact me directly.
Andrew G. Kireta Jr.
National Program Manager
Copper Development Association Inc.
P.O. Box 940
Franklin, IN 46131
Your contact for this case is: Andy Kireta Jr.