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What Causes Pinhole Leaks in Copper Pipes?

As a homeowner, keeping your house in tiptop shape is a main priority. Unfortunately, stuff happens that we can’t always expect or be prepared for.

Water heaters break down, sinks clog, pipes burst—all that and more can spin out of control if you don’t know what to look out for. Then, sooner or later, you’re looking to repair or replace your water pipes before ever knowing the signs.

According to Home Advisor, replacement plumbing costs can be as high as $2,000 on average. When it comes to pinhole leaks, a small problem can come at a heavy price. Though pinhole leaks are difficult to detect early on, it’s important to understand what you’re working with before reevaluating your entire plumbing system. 

Thankfully, you have options. 

In this article, we’ll go over what pinhole leaks are, how they happen, how to identify them, and a few different ways to fix them. 

What Are Pinhole Leaks?

In the world of plumbing, pinhole leaks are silent assassins. As the term implies, pinhole leaks are small leaks—often no larger than the head of a pin—that drip and pool over time. Due to their size, early detection is unlikely. 

A pinhole leak can go unseen for weeks, possibly months, allowing the damage to grow while the cause remains unknown

Pinhole leaks are also exclusive to copper piping. Without proper assessment from a plumber, leaks of this kind can severely damage your home and water system, resulting in hundreds to thousands of dollars in water damage.

What Causes Pinhole Leaks in Copper Pipes?

Copper water pipes are widely used due to the availability and reliability of copper. However, like steel or iron, copper corrodes and weakens. In the case of pinholes, several factors may contribute to corrosion and eventual leaks. 

Pinhole leaks in copper pipes can be caused by internal pitting corrosion, rusting, aging, and exposure. Let’s take a look at each of these in more detail. 

Internal Pitting Corrosion

Internal pitting corrosion is the leading cause of pinhole leaks. In this case, a leak may signify a breaking point in which extensive corrosion has eaten away at the inside of copper pipes. The damage will surface as small, random clusters of corrosion along the outside of copper pipes. Here, leakage may sprout if left unchecked. 

The exact cause of internal pitting is unknown. Most likely, a combination of water chemistry (pH levels, minerals, soft and hard water) and water turbulence (high/unstable water velocity) accelerates internal corrosion in some copper pipes more than others.


Chemically speaking, copper does not rust. Only iron does. However, copper oxidates and corrodes. What you think is rust is probably signs of external corrosion on your pipes, which could be an indicator of pitting, age, or exposure. 

Unlike rust, copper corrosion is gradual and slow. If you spot “rust” and are experiencing plumbing problems such as a drop in water pressure, you may have a pinhole leak.


The great thing about copper is that it’s durable. For residential plumbing, well-maintained copper piping can last up to 20 to 50 years, or more. In commercial and city-wide water systems, it’s double that amount. As a result, pinhole leaks are most commonly found in older plumbing systems and homes.

If your home or copper pipes are over 20 years old, it’s likely that is the reason why you might be experiencing a pinhole leak.


As mentioned above, copper corrodes over time, but short-sighted installation can hasten the process along. Due to dissimilar chemical structures, when in contact with rebar, copper can corrode in a process called galvanic corrosion. Likewise, concrete and soil may contribute to corrosion. 

Although copper is lauded for its hardiness, oxygen levels in soil can corrode underground or buried installations. Meanwhile, copper is unlikely to react with concrete, but high levels of sulfur in certain concrete mixtures can prove too acidic for copper, leading to weakening and leaks.

How to Identify Pinhole Leaks

Although potential leaks may sound like a nonissue if the piping is submerged in dirt or encased in concrete, water will gradually pool and penetrate any crack or breach. The result? High water bills and invisible damage that’ll ultimately crop up—at a high cost. 

If you suspect you have a leak, here’s what to look out for:

  • Discolored copper pipes: Copper degrades slowly. A good indicator of age, and therefore reliability, is discoloration. If your pipes have acquired blue/green-ish stains or tints, they’ve likely reached the end of their shelf life and are susceptible to pinholes.
  • Sounds of water dripping when faucets are all off: Since pinhole leaks are so small, they’re hard to see but easier to hear. Listen for the sound of running or dripping water when all the faucets are off. Depending on how sound carries through your house, a leak may remain undetected until a professional can personally examine the piping.
  • Mold/mildew smell permeating throughout the house: A leak, even a minor one, can lead to mold and mildew. If a room in your house has acquired a damp smell, you may have a leak. Examine your walls and ceiling for black or white splotches; this will be the source of the smell and possibly the leak.
  • Water stains on walls or floors: Aside from mold and mildew, there may be other visual signs of a water leak. Walls and flooring are likely to absorb water damage, so watch out for peeling, warping, cracks, and discoloration. These spots may also be wet to the touch.

Your Options to Fix Pinhole Leaks in Copper Pipes

Option 1: External solder

Depending on the location and extent of the damage, you may “patch” a leak. Soldering is similar to welding. However, rather than welding a pinhole shut, a filler alloy (the solder) is fixed at and around a leak, like a cuff. It is then fused shut with a blowtorch. 

Solders are typically made with copper and tin, so chemical compatibility shouldn’t be a concern.

Option 2: Replace the affected area with new copper piping

You may also replace the leaky pipe with an entirely new one. To cut, remove, and install a new copper pipe, a section of the wall, ceiling, or floor will need to be opened up. After the appropriate measurements are made, the new pipe is installed by soldering the pipes together, much like in the “patch-up” method.

Option 3: Replace with PVC pipe or other material

Alternatively, you could replace the damaged pipes with a PVC pipe or similar material, such as a CPVC pipe. PVC pipes are essentially plastic pipes. They’re widely used in plumbing due to their durability, low production, and low installation costs. CPVC is related to PVC, though chemically dissimilar and better used for hot water installation.

The great thing about plastic is that it never corrodes or pits, avoiding pinhole leaks altogether. However, due to the limitations of plastic, PVC and similar pipes cannot be applied universally. Furthermore, not all building codes accept plastic piping.  

Option 4: Completely repipe

If your copper pipes are over 20 years old, it may be time to consider a complete repipe job. Replumbing might sound intimidating, but if your pipes are old, they’re prone to leaks. If they’re prone to leaks, they’ll require frequent repairs. Compared to an odd few leak-less months, repiping your home can be a cost-effective alternative, buying 20 to 50 more years of good plumbing. This option, however, is likely the most expensive.

Option 5: Epoxy putty

If you’re looking for a quick fix, apply an epoxy putty over the leak. Epoxy putty is an adhesive, waterproof filler used to seal holes. To apply, first turn off your water supply and drain the leaking pipe. Once the pipe is dry, apply the putty according to the product’s instructions. Allow it to cure. If correctly applied, it should prevent further leaks. 

Remember: Putty is temporary. 

It will eventually wear down and the leakage will probably return. Fortunately, an epoxy-based coating can be utilized as a permanent fix—and not just for a leak, but for your entire plumbing system. 

The Best Option: ePIPE epoxy coating

While sealing a leak or replacing the section of damaged pipe may fix the problem quickly, what’s to say there won’t be more? 

Prevention is key. 

Get the most out of your copper plumbing with our epoxy protection method. Our patented epoxy coating process not only prevents future leaks but water contamination and lead leaching. It’s also completely safe for drinking water. Quick and far less destructive than traditional replacement and repair methods, you’ll have your water turned back on in a day! 

Once a small section of the wall/flooring is opened up, we dry and clean the pipes. An epoxy coating is then applied, lightly coating the inside of the damaged pipes. This creates a strong internal barrier, resulting in a practically brand new pipe. After a two-hour cure time, you’re done. No massive destruction to your landscaping, floors, ceilings, or walls. No long displacement time, either—you can stay inside your home during the entire process.

Best of all? Our epoxy coating solution is a cost-effective and more permanent alternative. That means more leaks or corrosion for a price that won’t break the bank.

Prevent Pinhole Leaks With ePIPE

As a home or business owner, the last thing you want is an unexplained spike in water bills. Worse yet if the leaks keep happening and your insurance falters. 

You can spend anywhere between hundreds to thousands of dollars repiping your property.

So why not get ahead of the curve and save yourself a headache with ePIPE?

Thanks to our extensive experience, our epoxy coating method is proven to prevent future pinhole leaks, lead leaching, and premature corrosion. We offer affordable pricing and reasonable payment plans for homes and businesses. 

Contact us at ePIPE today and you can upgrade your copper pipes without the headache or excessive price tag!