This is not "home" improvement per se, but it fits the spirit of this stack exchange. While waiting for my train I was peeking into a ceiling that had all of its slats removed for some kind of installation. I noticed there was a lot of new electrical conduit being laid which was made of copper. This struck me as really odd because this stuff is usually laid as aluminum or some kind of steel; copper is really expensive, it's not rust proof, nor is it electrically or thermally insulating, so I'm not understanding the choice in a more expensive material. The only answer I can possibly come up with it's better for its environment (moisture, against concrete; something re: anodization)

Here's an extremely professional photograph of the aforementioned:

enter image description here

Why would this be done?

  • 1
    Bizarre to say the least. Maybe the foreman is banging for disability. It's also bizarre to see PVC used as a conduit for network cabling.
    – mike
    Nov 4, 2013 at 4:50
  • " it's not rust proof" ? Copper does not rust, it will oxidize and form a patina. Hundreds of millions of homes in America alone have copper WATER pipes precisely because it does not rust. As long as the water that it comes in contact with has a relatively neutral PH it will last for decades if not longer.
    – Alaska Man
    Sep 22, 2017 at 18:07

4 Answers 4


I'm guessing it's plumbing, not conduit. Unless you actually see wires running through the tubing, I'm not convinced it's conduit. In the US only certain types of conduit are listed for use, and I'm sure they are similar in Canada. Copper is not among those listed, so it's not likely it would be approved by an inspector.

In a comment you mentioned that the pipe was connected using "nuts", and therefore could not be used for water. However, I disagree. A union is a fairly common fitting in plumbing. In fact, you'll probably find some if you look at the plumbing for the water heater in your house.

enter image description here


After further searching National Electrical Code, I found this...

National Electrical Code 2014

Article 344 Rigid Metal Conduit: Type RMC

II. Installation

344.10 Uses Permitted.
(A) Atmospheric Conditions and Occupancies.
(2) Red Brass RMC. Red brass RMC shall be permitted to be installed for direct burial and swimming pool applications.

(B) Corrosive Environments.
(1) Galvanized Steel, Stainless Steel, and Red Brass RMC, Elbows, Couplings, and Fittings. Galvanized steel, stainless steel, and red brass RMC elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.

(C) Cinder Fill. Galvanized steel, stainless steel, and red brass RMC shall be permitted to be installed in or under cinder fill where subject to permanent moisture where protected on all sides by a layer of noncinder concrete not less than 50 mm (2 in.) thick; where the conduit is not less than 450 mm (18 in.) under the fill; or where protected by corrosion protection and judged suitable for the condition.

Which means it's possible the conduit is not copper, but red brass. According to wikipedia, red brass may be 85% copper, 5% tin, 5% lead, and 5% zinc.


I can think of two possible explanations:

  1. It could be brass conduit. These were once used to wire submerged swimming pool light fixtures. Maybe an electrician had some left over and used it where it wasn't necessarily required.

  2. It could actually be copper plumbing in a water-related use, such as to provide hot weather cooling for the roof above, or supply sinks somewhere.

Can you see what is at the ends of the conduit?

  • 1
    Definitely not water related. Segments were connected with nuts. I never considered brass, but it definitely had that characteristic coppery orange tinge
    – BB ON
    Nov 4, 2013 at 0:37

Alright, I took another look and it was definitely electrical. There were junction boxes branching off to the ceiling lights. Turns out it's original 60's era conduit and not new; just in good shape. Since then, buildings standards and material costs have changed drastically making it uneconomical to use.


It's most likely something like Pyrotenax. Copper covered fireproof cable.

  • Sounds like an answer to me. Question: Why would they do this? Answer: to make it fireproof. I don't think that's likely the case here, but it is a direct answer. Sep 24, 2017 at 16:08

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