Pinhole Leaks In Copper Water Pipes: Their Causes And How To Repair Them

Posted on: 5 March 2015


Copper is considered by many to be a material of choice for water pipes, as it has several strong, positive characteristics: it is easy to work with, resists rust and has natural antibacterial qualities. Because of this, copper is the predominant material used for water pipes in homes and businesses in the United States for the past several decades. However, copper does possess a disadvantage that has proven to be frustrating—it is vulnerable to pinhole leaks that are capable of causing significant damage. These pinhole leaks can cause mold growth, damage drywall and create wood rot. Below is more information on what causes pinhole leaks, how to locate them and how you can address them:

The causes of pinhole leaks in copper pipe

Pinhole leaks are nearly microscopic holes that develop in copper pipes and tubing. Technically, pinhole leaks are a form of pitting corrosion which only occurs in localized areas. That means pinhole leaks can be widespread throughout a plumbing system, but they are unlikely to be found in clusters.

Pinhole leaks are almost imperceptible to the human eye, but their effects are much larger in scope. Pinhole leaks are caused by circumstances that are not yet clearly understood, though potential causes are being explored by researchers.  Some of the specific possible causes include:

  • Water chemistry - It is known that pinhole leaks affect community groups that share the same water supply, so it is likely that pinhole leaks are caused by certain types of water chemistry. One suspected agent is chloramine, a chlorine-substitute used to disinfect drinking water, as it is known to be corrosive to copper.

  • High velocity water flow - Pinhole leaks seem to occur more often when the pipe's water flow rate is high. Rapid flow rates scour the inside of the copper pipe and make it vulnerable to other agents that pit the metal.

  • Corroding hot water heaters - Hot water heaters contain an anode that helps prevent corrosion inside the tank. However, as the anode slowly disintegrates, its particles are distributed throughout the water pipe; these tiny pieces of metal will settle and react with the inside lining of the copper pipe. This corrosive reaction may cause pinhole leaks.

Finding and fixing pinhole leaks

Pinhole leaks are not always easy to locate, especially when they only drip once or twice per hour, and that increases their potential to cause slowly escalating damage. By the time pinhole leaks are found in a lot of instances, extensive damage may have already occurred. However, there are a few clues that can help you locate pinhole leaks before they have a chance to ruin your home:

  • Discolored copper - If you are able to view your copper water pipes, then look for small bluish-green spots. Unless the pipe has been exposed to other water sources, there is a good chance that a pinhole leak has formed.

  • Bubbling paint - Wall or ceiling paint that begins bubbling for no apparent reason may be due to moisture exposure. You may need to drill a hole in the vicinity of the bubbling to check for moisture; just be sure to drill slowly so you don't puncture any hidden pipes.

  • Moldy, musty smell - If you start to notice an odor that is musty or moldy, then you should check for leaks. Look in your attic and basement for damp insulation that has become a growth medium for mold. Also, be sure to check carpeting in closets and other out-of-the way locations; these areas may be harboring moisture from a leaking pipe.

Once you have located a pinhole leak in a copper pipe, you have several possible options for repair. However, your first priority should be to stop the leak while you explore your alternatives. A hose clamp wrapped around a piece of thin rubber is a good option for patching pinhole leaks:

1. Choose a clamp that is at least a half inch larger in circumference than the pipe, and unscrew it completely so the band is detached from the tightening mechanism.

2. Next, wrap the band around the pipe, and loosely reinsert the band into the tightening mechanism; however, don't tighten it just yet.

3. Cut a small piece of sheet rubber, such as a section of gasket material or bicycle inner tube, and slide it between the band and the pipe so they both cover the pinhole leak.

4. Position the rubber and hose clamp, and tighten the screw until the clamp is firmly in-place. Be careful not to crush the pipe with the clamp.

After you have stabilized the leaky pipe, you will need to consult with a plumber like Shakley Mechanical Inc regarding your options. In some circumstances, the network of copper pipes may need complete replacement if the problem is systemic. In that case, PEX plastics are an alternative worth considering since they are highly resistant to corrosion and other breakdowns of the material. Others may recommend PVC pipe, but be sure to get a variety of opinions before making a commitment.