DIY Plumbing Tips: Fix Pipe Leaks

Copper is the most commonly used plumbing material in the United States today, installed in more than 80 percent of all homes and office buildings in the U.S. Relatively inexpensive and easy to use, and known for its resistance to contamination and corrosion, copper is used for pipes and numerous other plumbing fixtures. Unfortunately, however, notwithstanding excellent resistance, copper pipes are not immune from springing leaks over time, resulting in costly damage.

The most common reason for a copper pipe to leak is due to pitting, a form of corrosion that occurs in both soft water and hard water environments, and attacks small, localized areas on the inside wall of the pipe. While much research has been conducted in this area, the exact reason why pitting type corrosion occurs remains unknown. It is, however, generally believed to be due to a chemical reaction between the water and the copper, and has been classified into one of three categories (Type I, Type II, and Type III Pitting) based on water temperature and pH level. Type I occurs place in cold, hard water with average pH levels between 7.2 and 8.0. Type II occurs at in warm, soft water with pH levels that are less than 7.2. Type III occurs in water that is cold, and soft with high pH levels. A pinhole leak occurs as the final stage (and breakthrough) of an area of the pipe affected by pitting.

A second reason why a copper pipe may leak is the use of poor quality materials in building, such as a builder using lower grade copper, or pipes of a smaller diameter than necessary.

A third reason for leaking copper pipes is that, in installation, plumbers sometimes take shortcuts that compromise the pipes. One example is a technique known as "cold bending" in which, rather than using elbow joints, the plumber simply bends the pipe to make turns. At the bend, the copper is weakened and over time, water will cause the pipe to erode, eventually resulting in leaks.

While the second and third reasons stated above can (and should) be eliminated in the building and plumbing installation process, it is, unfortunately, virtually impossible to prevent or stop copper from pitting. By taking the following steps, however, it is possible to reduce damage caused by the leaks induced by such pitting:

Check all copper piping that is exposed for small stains of a bluish-green color, which is one potential sign of a pinhole leak. Upon first noticing any such leaks, call a licensed plumber immediately to determine if there is, in fact, a leak. Note: Such bluish-green stains can also be found on copper pipes in damp environments, such as basements, so such stains do not necessarily indicate a leak.

Purchase pipe clamps, and install over pinhole leaks, until a plumbing contractor can perform a more permanent repair. Such clamps are available for purchase at any hardware or home repair store.

Unfortunately, however, other than replacing the damaged section of the pipe completely, a job best left to a licensed plumber, there is no permanent solution to a pinhole leak resulting from pitting corrosion. Nor are there any certain prevention techniques to keep such pitting from occurring in the first place.

Cast Iron Waste Pipes

here's a crack about 8" long on the top of the large iron sewer line that runs through my basement. The surface of the pipe has some brownish-orange rust, but it seems to be a very thin coating. Before I call a plumber, I'm trying to do some research to determine if this is a sign that the entire piping system might need replacement. How long do these pipes last? Any insight would be appreciated.

About a dozen US cities possess cast iron pipes that have supplied water for over 150 years. Hundreds have cast iron water mains over 100 years old. Cast iron pipes used for waste piping, however, are subject to corrosive action that pipes carrying drinking water are not.

The external rust, unless showing deep pitting, is common and probably not a concern. I've heard of only a few cases of underground waste lines failing from external corrosion as a result of being in contact with unusually acidic soil. When cast iron waste pipes fail, it's usually due to corrosion from within.

As a result of what runs through waste lines, hydrogen sulfide gas can form. This can oxidize and produce sulfuric acid, which corrodes cast iron. Some drain cleaners also contain sulfuric acid and, if used continuously, can accelerate the corrosive action and shorten the life of the cast iron piping system.

When examining cast iron piping, you'll typically find two different signs of failure. One is the crack that you describe, usually forming on top of the pipe or at a seam, created by the form used during the casting process. This is likely due to the hydrogen sulfide gas collecting in concentration and the resulting acidic attack weakening the pipe wall.

The other external indication of failing cast iron pipes is blobs of rust, usually found on the underside of horizontal sections. The size of these blobs can be anything from little pimples to about the size of half a walnut shell. These aren't as obvious as cracks and can be overlooked because they don't perpetually leak. As the iron around a pinhole rusts, the iron expands and seals the leak. While they might not be actively leaking when discovered, it's certainly a sign that internal corrosion has breached the wall of the pipe.

The old method of casting pipes, called the "pit-cast" method, can leave variations in the thickness of the pipe walls. The thinner-walled portions might be the first to show cracks or pinholes, but there are likely other areas of corrosion that just haven't surfaced--yet. Although more common, this corrosion isn't limited to the horizontal sections. Cracks, pinholes and rust blobs can appear on vertical sections as well.

Some homeowners, and occasionally some professionals, insist that patching a pipe that has cracked or developed a pinhole is an acceptable and permanent repair. Based on my experiences, I disagree. I recommend the section of pipe showing any sign of failure be removed and replaced by an experienced plumber. While the repairs are being performed, the adjacent sections can be evaluated. If the walls are getting thin from corrosion, removal and replacement of these sections is advised.

Pitting Corrosion on Metal Surface

Pitting is one of the most destructive forms of corrosion as it will potential cause equipment failures due to perforation / penetration. pitting generally occurs on metal surfaces protected by oxide film such as Stainless steel, aluminum, etc. Typically for boiler and feed water system, pitting corrosion rate increase dramatically with the increase of oxygen content in the fluid.

Pitting can occur in any metal surfaces. Following are some pictures of pitting corrosion.