Thursday 15 July 2021

What Are Pinhole Plumbing Leaks?

Posted by at 12:11 AM

Copper pipes will typically last 20 or more years, but can commonly run afoul of pinhole leaks.  These leaks occur only in copper piping and under the right conditions can happen fairly rapidly.  If your home has copper pipes, you need to be aware of what a pinhole leak is, the signs of a leak, and how to prevent them. 

What is Pinhole Leak?

As the name suggests, a pinhole leak is a leak in a copper pipe caused by a pin-sized hole in the pipe.  Typically, these holes are less than 1/8 inch wide.  Although very small on the outside of the pipe, a pinhole leak is actually a sign of a much larger corrosion problem inside the pipe and a symptom of long-term corrosion damage.  This means that pinhole leaks are not only a problem in their own right, but a problem as they pertain to the larger damage hidden behind them.

Signs of a Pinhole Leak

There are several tell-tale signs that you’re dealing with a pinhole leak.

  • Increased Water Bill: No matter how small the leak is there will be an increase in your water bill.  Keep an eye on your bill and take note of any unusual fluctuations.
  • Decreased Water Pressure: Water isn’t the only thing you lose in the presence of a pinhole leak.  When a pipe has a hole in it, no matter how small, the pressure inside the pipe decreases, which can decrease water pressure throughout your home.
  • Visible Damage: If your pipe has been leaking for a long time undetected, you’ll eventually begin to see visible signs of water damage to the materials under and around the pipe.
  • Mold and Mildew: Pinhole leaks are notorious for causing mold and mildew growth because they often occur inside the wall where they go undetected, creating the ideal environment for growth.
  • Dripping Sounds: Unexplained dripping noises in the home are a more obvious sign of an undetected pinhole leak.
  • Pipe Discoloration: The exterior of your copper pipes should always look copper-colored.  If you’re noticing brown, green, or blue discoloration, that’s an indication that the pipe is oxidizing in the presence of leaking water.
  • Condensation: Like discoloration, the outside of your pipes should never be moist or wet.  Wet pipes can be caused either by the leak itself or by condensation from the leak. 

While there are many potential symptoms of pinhole leaks, bear in mind that they are notoriously hard to locate because they’re so small and can occur anywhere along the pipe, even inside the wall cavity.  One surefire way to determine if you have a leak (although not to pinpoint the location) is to turn off your water supply and check your water meter.  If the meter is still moving after you’ve shut off your water, you have an undetected leak somewhere in your home.

Causes and Prevention

Pinhole leaks are caused by something called pitting corrosion, which simply means corrosion that causes holes in the material.  There are several types of pitting corrosion and being aware of them can help you prevent them from happening. 


The first and most likely culprit for pinhole leaks is chemical damage to the copper in the pipe.  While the pH of your home’s water doesn’t vary enough to impact the quality for human consumption and use, it can affect your pipes.  Through various chemical interactions depending on the pH and makeup of your local water supply, simply using your plumbing can result in chemical reactions that will eat away the protective coating that insulates the interior of your pipes.  The areas where this coating is worn away will be immediately susceptible to corrosion and resulting leaks.  Extremely hard water is notorious for this type of damage, so investing in a full house water softener and keeping up with its routine maintenance is one way to help prevent pinhole leaks.


Similar to damage due to the chemicals present in your water supply, copper pipes can be damaged by physical contaminants such as sediments and heavy metals.  These contaminants will physically wear down the inside of your pipes as they pass through.  This type of damage is also common with very hard water as well as with well water and abnormally high water pressure.  Again, a properly functioning water softener can help remove some of these contaminants.  Monitoring your water pressure to ensure it doesn’t get too high can also help. 


A less likely cause of pinhole leaks is localized damage due to low quality pipes or improper installation.  Pipes that were retrofitted or not installed professionally are more susceptible to this type of damage because they will not be able to resist corrosion as well as new, properly installed plumbing.  Damaged pipes should be replaced as soon as possible by a professional plumber.


Another less likely cause of pinhole leaks is a lack of uniformity in the plumbing.  Pipes that were retrofitted or only partially replaced may run into this problem.  If your copper plumbing is attached to another type of metal or with a joint of a different metal, these metals may interact because water is a solvent.  If you home has very old plumbing and outdated joints and segments of pipe need replaced, make sure to call a certified plumber to help.

Pinhole leaks are very small leaks that can cause very large problems because they so often go undetected.  Knowing the causes, signs, and how to prevent these leaks can help you keep your home safe from leaking.