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topic 25718

Copper pipe is turning black

A discussion started in 2003 but continuing through 2019


Q. We have a subcontractor who brought some copper pipe into a basement on one of our jobs. Within 2 days or so, the outside of the pipe has turned black but the inside has not. Why would this happen? Does this mean there may be an oxygen deficient atmosphere?

Rob Carson
Construction company - Salem, New Hampshire


Q. I'm a heating/plumbing service guy. Approx. 14 months ago I installed a hot water boiler in the cellar of a home and upon returning for a service call this past week, I noticed all the new shiny copper piping had turned black. A sort of deep dark blue black, black.
The other strange characteristic is this particular cellar has always had a strange chemical odor, acidic smell. I advised the homeowner to have the cellar tested by an environmental testing lab. In my 15+ years in the heating/plumbing trade, I have never seen copper discolor like this or change color so dramatically in such a short period of time.
The pipes stay dry and vary in temp. from room temp to 180 °F. Any ideas on what might cause this? Thanks

Bill Knott
heating, plumbing, air cond. tech - Cobleskill, New York


A. I would suspect exceptionally high sulfide levels. Is the strange smell anything like rotten eggs?

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


Q. I just happen to have the same problem that the people in the letter from Mr. Bill Knott has. I have no idea how to fix this problem. I have a boiler and all of my copper pipes are turning that blue black, plus the odour. Any help, suggestions that anyone could give me on solving this problem would be a blessing like you would not believe.


Lesley Pentland
- St.Catharines, Ontario, Canada

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July 12, 2008

Q. I have the same problem, copper pipes turning blue, and a rotten egg smell, does anyone have any ideas?

phil cynvery
- Little Ferry, New Jersey

August 17, 2009

A. Could be Chinese drywall.

David Johnson
- New Orleans, Louisiana

thumbs up sign > Hi David. Please flesh out your implication -- we have heard about this problem in general but we don't know any details. Thanks!


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

February 11, 2010

Q. Black copper pipes. Found in close proximity to basement sumps that collect water softener waste water (salt cleaning mixture). Cold water lines only. Homes have well water with some sulfur content in test samples. This is a chemical reaction. What I don't know is if the reaction is damaging the integrity of the pipe and sweat joints.

Bill Butts
Handyman - Grand Rapids, Michigan

August 19, 2010

A. I just moved into an 8 year old house and the copper pipes are black. Even the shower valve and pipe inside the wall. There was a rotten egg smell too. I don't know if this is the cause, inspection, I found that there was a small gas leak on the water tank heat control and another on a union. Repairing the leaks took care of the smell. Not sure if it was the cause of the black pipes. Also, the dryer vent was discharging into the basement, so that could also be a source of chemical to blacken the copper.

Dennis Pare
- Edmonton, Alberta, Canada

September 16, 2010

A. In 20 years of being in the Plumbing Service & Repair Industry I have ran across this blackened copper pipe problem before, Here is what I have found out ...
About 15 years ago in Stanton Ca I was called out to a small townhome community to repair a bunch of leaking pipes, copper water pipes, there were leaks on the main runs on some units, others were on branch lines feeding fixtures and Water Heaters, etc.

Well I attempted to repair on these lines, being careful to clean and prep each repair section ...
This pipe was almost impossible to solder.
After talking with others that had come across this problem before, I was told that Most of this pipe was imported from either China or Korea back in the 70's.
This pipe was very cheap and saved vendors and builders lots of money. The bad part about it is this pipe is so full of impurities that these impurities come to the surface as the pipe ages, so trying to solder it is like trying to solder galvanized pipe!
To this day there are still many tons of this pipe in warehouses throughout the U.S and it still makes it way to plumbing supply yards and home improvement stores.
One Job I was involved with the insurance company paid to have the building repiped in GOOD copper pipe. That copper pipe that turns black is substandard pipe with many impurities.

Keith H [last name deleted for privacy by Editor]
- Denver Colorado, USA

January 21, 2012

A. I bet my bottom dollar this is caused by counterfeit cheap Chinese copper pipes. This will turn the water blue and stain the bath/sinks, etc.
A brand new school in my town has had to provide bottled water for the last 5 years because of Blue Water.

Alan Dransfield
- England

April 14, 2017

Q. The question WHY water pipes turn black INSIDE has not been answered: please do so. All of our water pipes (installed in the 1970's) are totally black inside: why?

Dirk Holger
private home owner -- tapestry artist - olney, maryland, usa

April 2017

A. Hi Dirk. At least two possible causes were cited -- namely sulfur in the water and/or cheap Chinese pipe that looks like good copper pipe, but actually isn't (too much zinc and other tramp materials).

I don't think anyone can offer a definitive answer of which of several possible causes is THE cause from the single data point that the inside has turned black. But if you tell us whether you have city water or well water, what the water analysis says, whether other homes in your neighborhood were piped/re-piped at the same time, whether your neighbors report similar problems, whether your water is ever blue, if there are blue stains on the porcelain, etc., maybe someone can be at least a bit more definitive. Good luck!


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

April 14, 2017

A. I wonder why should copper pipes be used for household plumbing- I thought it is too expensive. We normally use GI pipes and recently HDPE. Copper pipes are used in heat exchangers because of it good thermal conductivity. It is not difficult to analyse the contents of the pipes used and tally with what the manufacturer had promised. It is unfair to blame Chinese without doing proper homework!

H.R. Prabhakara
Bangalore Plasmatek - Bangalore, Karnataka, India

April 2017

A. Hi, H.R. -- Copper is surely the most widely used water piping material in the USA, although plastic pipe of various types is increasingly popular. Opinions about the safety of GI water piping vary here. As noted, we don't yet know whether Dirk's issue is due to excess sulfides in the water, low quality pipe, a little of both, or another cause.

opinion!  It is not improper for Keith and Alan to mention the fact that cheap, low quality, Chinese copper pipe and wallboard have been responsible for a lot of problems. It's not a matter of blaming another country ... but simply acknowledging the that there will always be scammers ... and if you build a distribution system which obfuscates the source behind layers of import/export complexity and multiple languages, and you make 'salad', you should expect scam products.
I recently bought a box of screws and -- instead of it saying "made in China" or "made in Indonesia" or "made in USA", it said: "made in one or more of the following countries (followed by a list of a dozen countries). It's not just the Chinese source to blame, but the distributors, warehouses, and builders who buy & install materials of dubious origin, and make things virtually untraceable while major damage is being done. And YES IT IS DIFFICULT for the average home owner to determine what specifications copper pipe should meet and to determine whether the pipes in their homes comply.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

December 16, 2018

! We have some copper pipes in our basement that were installed a few years ago. They were copper-colored until a few months ago when we started having some issues with a sewer gas smell in that part of the basement. I highly suspect that the sewer gas had something to do with the color change.

David Masteller
- Wheeling, West Virginia USA

sidebar2 March 12, 2019

Q. What will remove the black?

Geoff Sykes
Restoration antiques - England Great Britain

March 2019

A. Hi Geoff. More words please! Because of your stated involvement in antiques, I'm guessing your interest is not removing the blackening on the pipes in your basement which the other readers have been discussing, but black coloration on antique something or others which you believe are made of solid copper?

Do you know whether it's a deliberate blackening? Is so, there is probably a lacquer or clearcoat you'll need to remove with a solvent first. If all the surfaces are reachable, the blackening can then be polished off (assuming the copper is not just a thin plating which might also polish off). More details please. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

December 10, 2019

Q. Hello. Same thing here after 8 years in the hours a sulfur /sewage smell has arisen and all copper pipes in the basement are now black. I noticed the smell increases when the sump pump runs. Any thoughts?

Heath Achatz
Homeowner - Casco Michigan usa

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