Oxidation on Copper Gas Line

Line feeds a gas water heater. Can anyone tell me the reason for this oxidation? If it was a water pipe, I’d know the answer. Thought it was unusual for gas.

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Should be in plumbing section. Sorry!

My guess is lack of proper cleaning after the soldering process.

…or, if those joints aren’t 100% gas tight, a leak will be present, propane and n.g. are realy realy cold when the run threw the pipe, and when they leak, condensation will occur and there’s your moisture, maybe?

i like that too, acid in the flux will cause the same thing sometimes.

I like Bruce and Jay’s answers.

3/4 inch copper line for gas with joints??? Wow…

You won’t see that in my area. 1/4 inch copper tubing (with no joints) is the maximum I see in Massachusetts.

Is that piping legal in your area?

Maybe they should have used threaded black iron.

I’ve never seen copper used for gas in any of the states where I have worked.

I’m with David on that one.

that is a hazard waiting to happen!


Copper tubing is a norm in the United States.

Here’s some learning material for ya…

](Applications: Fuel Gas)

Found this on that site: “In addition to mechanical joints, or in many cases instead of mechanical joints, brazed joints utilizing ASME/ANSI B16.22 wrought copper fittings may be used in copper gas distribution systems. When brazed connections are required, they should be made using a brazing alloy with a melting point above 1,000 F. **The brazing alloy must contain less than 0.05% phosphorus.”

**So, do ya’ll think the fittings are a concern? It’s crunch time for me on this report.



One cannot enter a simple No. on our new message board. Has to be at least 4 characters, and spaces apparently don’t count as characters.

This new message board and its rules are, quite frankly, irritating and stupid in some cases.

If this 3/4 inch copper pipe was on my inspection, I would be recommending a plumber to evaluate.

I would also, not because of the fittings, but because it’s copper tubing being used as a gas supply line. The plumbers here would be replacing the copper gas supply line with galvanized iron or black steel.

Please tell me exactly why that is?

Joe, it could be type k which is ok or it could be other types.
type k has a thicker wall.

Its just not visible on most inspections and I would not be concerned with it really because it could be type k.

All types of copper is ok for propane.

I would report the oxidation as being present.

As I stated earlier…

In the hundreds of inspections I’ve performed, I’ve never ran into 3/4 copper supply line (esp. with joints) in Massachusetts. We use 1/4 copper tubing (no joints) and black steel.

SC may have different codes relating to gas supply line material.

I simply do not like what I see…

It appears that the line was soldered as opposed to being brazed. I would call for evaluation as well. I beleive SC requires this line to be brazed for gas service. The 3/4 inch line might be required for the proper gas flow depending on the size and BTUs of the water heater.
Regards Bill

If this is a gas supply line? (Gas or Water?) 3/4" is too big for residential needs!?

  1. Copper can be used in LP.
  2. Fitting is not needed. Pipe can be bent.
  3. Silver brazing is required.
  4. Fittings/splices should not be made in an enclosed space.

The oxide your are asking about is flux as posted above.





The oxidation is caused by oxygen, the situation has been exacerbated by improper cleaning of the joints after Brazing.:slight_smile: