green pipes

What causes copper pipes to turn bright green in some spots? Is it an electrolisis problem?

Wow! great site I am just printing the book on Copper all 57 pages .
Thanks, This NACHI group just keeps going and going ,So glad to be small part .
Roy Cooke . A HAPPY NACHI Member

Copper will also turn green at the fittings if the plumber did not wipe off the excess flux after soldering.

Thanks for your reply, that’s a great website on copper. But maybe I asked the question wrong. Where the ground is connected to the pipe, from there all the way to where the pipe penitrates the outside wall, the pipe is green. Everything seems to be bonded correctly, is this a grounding problem?

Many chemicals can cause copper to discolour Javex ,Horse Pee,and many more I can not think now getting tired Need a bit more information where is this copper .
Roy Cooke

There was a very good discussion on this condition back in 2001 or 2002 on either,, or Unfortunately, I don’t remember which one, and I don’t belong to CREIA or ASHI anymore.
Every time I have found the condition you describe, I explain to my Clients what it could be (all those scenarios noted above), and each time it has turned out to be a grounding/bonding/electrical problem.

Jae, great site…

I was asked in a private email to expound on my previous post. I was at a re-inspection a few years ago because I had noted the green pipes, told my Clients that I had no idea why they were green but would know within 24 hours, discovered the green pipe thread (at,, or, as stated previously). In the thread, many people weighed in stating that it was stray electricity running along the copper pipes. Electricity, of course, should not stray. In one house, the electrician found 17 volts running along the pipes; all other times it’s been down in the 4-8 volt range.

In one house, the first house where I had the problem, I had the privilege of being there with the electrician. We finally discovered the problem. The walls and ceiling was lathe and plaster. Up in the attic, there was an open and live electrical termination laying on the ceiling. That wire was shooting electricity into the ceiling where it was traveling through the walls and to the copper pipes that went through the walls and into the crawl space, where the voltage was low. It did, of course, indicate the more serious problem of a live wire termination in the attic. Imagine someone crawling in the attic and accidentally putting their hand on that live wire termination. I had noted the improper wire termination in my report, but I sure didn’t think that it could have anything to do with the copper water pipes being green. Also in that house, I detected low voltages in the ceilings, walls, door hinges, etc., but never dreamed that it was coming from a single live wire in the attic. Now I’m not sure that I could ever own a lathe and plaster house. Nah, I could. I’m not that paranoid, according to my psychiatrist, Dr Vicodin.

Were you walking around with a non-contact voltage detector in your pocket?

Hmmm…no jokes now, I was serious!:wink:

No. But perhaps not a bad idea.

The house had wood floors and I wear rubber-soled shoes, but when I touched doorknobs in that house, I constantly got shocked. Ergo, I pulled out the voltage detector. it’s called verdigris. Verdigris is the common name for the chemical Cu(CH 3 COO) 2 , or copper(II) acetate. It commonly occurs by the action of acetic acid when copper, brass or bronze is weathered and exposed to air or seawater over a period of time.

Not to be confused with pipes turning amber connected to ambergris.