Photograph of pipe condensation (C) Daniel FriedmanCorrosion & Leaks in Copper or Steel Water Pipes
Causes of metal water piping corrosion or leaks

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

What causes leaks in metal piping?

This article describes the many causes of leaks in metal water pipes. We list the factors that explain green corrosion on copper pipes, leaks at pinhole perforations, leaks at pipe joints, and other leak types on metal piping. The article also discusses the important role of water chemistry and even electrical grounding mistakes in the development of pipe leaks or pipe corrosion.

Some of these leak causes may also explain leaks in metal drain piping. Our page top photo shows a water line leak that's extra trouble to repair: a break in water piping between the building interior and the water main in the street. Some careful attention to the cause of the leak (once the line was excavated) helped avoid a repeat visit of the plumbers to this home.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Causes of Leaks in Metal Water Piping or Water Cylinders / Water Heaters

Green corrosion on copper water piping indicates a problem in this photo (C) Daniel FriedmanReader Question: green stains, corrosion, gritty material around copper pipes & pipe fittings or connections

(Jan 14, 2015) JohnGotts said:
What is the green gritty mineral buildup around some sweat joints in my boiler installation?
Can it be removed or should it be left alone?

30 January 2015 Sal said:
If your house water main is green near the electric ground connection does that mean the ground wire is going bad or is bad

[Click to enlarge any image]

Reply: common causes of corrosion on or leaks in copper piping

Copper pipes have been in wide use since the 1850's and have been produced by a variety of methods and in a variety of thickness ranging from heavy gauge to extruded thin-wall copper.

In the U.K. light guage piping came into wide use beginning in the 1920's. A thin oxide coating (CaCO3) that forms inside copper water piping helps resist corrosion by reducing further dissolution of the copper pipe from the interior as may other natural corrosion inhibitors - (Campbell (1994)).


Most likely it's an oxide of copper caused by corrosion. Look at it closely to be sure there are no leaks.

Watch out: never "pick" at or probe corrosion. A slow leak in metal piping may be just that, very slow, actually leaking through a pinhole where the piping material is quite thin.

When you scrape at or poke at such a corroded spot the risk is that you convert a small leak that would have given you time to hire a plumber into a big emergency leak that requires that you shut down the building water supply before making a call for emergency (more expensive) plumbing repairs.


Watch out: Green corrosion on a water pipe that is found only around the electrical ground is worth some further checking: stray electrical currents or improper grounding could be causing the corrosion that you see.

Water supply piping connection: copper to galvanize (C) Daniel Friedman

Some green corrosion on copper piping is common and may not necessarily mean a leak is present. For example we may see corrosion where solder flux ran out around a solder joint during pipe connections by sweating (copper soldering).

Other causes of green corrosion on copper pipes, besides an actual leak (see our comment to John in just above) are listed below.

Our photo (left) shows an ingenious temporary "repair" by a homeowner who observed a small drip at a badlhy-soldered copper water pipe elbow. As the joint was hard to reach he made a tiny funnel and drain to catch the drip and direct the water to a nearby laundry sink.

While we respect all clever midnight or Sunday Afternoon emergency building repairs, this is not a long term nor reliable plumbing leak fix. It was clever, though.

Photograph of pipe condensation (C) Daniel Friedman

Galvanized steel pipe rust and clog (C) Carson Dunlop Associates

Image above provided courtesy of Carson Dunlop Associates.

See GALVANIZED STEEL WATER PIPING for a discussion of the additional factors involved in leaky galvanized steel pipes.

At LEAK TYPES, WATER SUPPLY or DRAIN PIPES - we describe the types of leaks that occur in water supply and drain piping with an eye (or an ear) towards leak detection and towards hidden leaks in buildings

At REFERENCES for this article we include research citations on the various causes of corrosion on or leaks in building piping systems.


Continue reading at PLASTIC PIPE LEAK CAUSES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CORROSIVITY or ACIDITY of WATER and how water chemistry corrodes pipes or water heaters / water cylinders

Or see LEAK TYPES, WATER SUPPLY or DRAIN PIPES - where do leaks occur and how to find them


Suggested citation for this web page

LEAK CAUSES in WATER PIPING at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman