What causes pinholes in copper pipes?

Pinhole leaks in copper pipes are typically caused by corrosion from the inside out, creating tiny holes that can spray water and cause significant damage if not addressed quickly.

The most common cause is pitting corrosion, which occurs when your water chemistry is imbalanced. High acidity levels (low pH below 7.0) literally eat away at the copper from the inside. This is particularly common in Ottawa homes with well water or areas where the municipal water treatment creates acidic conditions. High chlorine levels used for water disinfection can also accelerate this corrosion process, especially in newer copper installations where the protective oxide layer hasn't fully developed.

Water velocity and turbulence also contribute to pinhole formation. Areas where water changes direction quickly - like at elbows, tees, or near the water heater - experience more turbulence that wears away the pipe's protective coating. Electrolysis can occur when copper pipes contact dissimilar metals without proper dielectric unions, creating electrical current that accelerates corrosion.

In Ottawa's climate, temperature fluctuations stress the copper, and homes built in the 1980s-2000s often used thinner-walled copper that's more susceptible to pinholes. The mineral content in our local water supply can also create conditions where certain areas of pipe corrode faster than others.

Prevention involves water testing to check pH and chlorine levels, installing water treatment if needed, and ensuring proper pipe installation with adequate support. If you're seeing multiple pinhole leaks, it often indicates a systemic water chemistry issue that will likely cause more leaks throughout your copper system.

Once pinholes start appearing, temporary patches won't solve the underlying problem. A licensed plumber should test your water chemistry and assess whether spot repairs or partial repiping with PEX is the most cost-effective solution for your Ottawa home.