What Causes Pitting Corrosion
Copper pipe corrodes internally through a process called pitting corrosion — small, localized points where the protective oxide layer inside the pipe breaks down, allowing water to attack the copper directly at that specific spot rather than wearing evenly across the whole surface. Several water chemistry factors influence how quickly this happens: pH level, dissolved oxygen content, chlorine or chloramine levels used for disinfection, water velocity inside the pipe, and mineral content.
Harder water — water with more dissolved minerals — tends to accelerate this scaling and pitting process over time. Torrance Municipal Water draws roughly 89% of its supply from the Metropolitan Water District’s Colorado River and State Water Project sources, both of which are harder than pure local groundwater. That’s a genuine, measurable factor in why pinhole leaks in original copper piping are such a common call throughout the city, not just an assumption.
Factors That Make It Worse
- Pipe age — original copper from the 1950s–60s postwar construction wave is now well past typical service life
- Wall thickness — Type M copper, with its thinner walls, develops through-wall leaks faster than Type L or K once pitting starts
- Water hardness — harder water accelerates internal scaling and pitting
- High water velocity — undersized pipe or high pressure can accelerate erosion at bends and fittings
None of this means your specific pipes are guaranteed to fail — plenty of original copper systems perform fine for decades. But if you’re seeing recurring pinhole leaks in different spots, these are the underlying factors worth understanding before deciding between repeated spot repairs and a full reroute.
Worried About Your Pipe Condition?
Copper Pipe Corrosion: Why It Happens
The real chemistry behind pinhole leaks — and why it’s more common in some Torrance homes than others.
What Causes Pitting Corrosion
Copper pipe corrodes internally through a process called pitting corrosion — small, localized points where the protective oxide layer inside the pipe breaks down, allowing water to attack the copper directly at that specific spot rather than wearing evenly across the whole surface. Several water chemistry factors influence how quickly this happens: pH level, dissolved oxygen content, chlorine or chloramine levels used for disinfection, water velocity inside the pipe, and mineral content.
Harder water — water with more dissolved minerals — tends to accelerate this scaling and pitting process over time. Torrance Municipal Water draws roughly 89% of its supply from the Metropolitan Water District’s Colorado River and State Water Project sources, both of which are harder than pure local groundwater. That’s a genuine, measurable factor in why pinhole leaks in original copper piping are such a common call throughout the city, not just an assumption.
Factors That Make It Worse
- Pipe age — original copper from the 1950s–60s postwar construction wave is now well past typical service life
- Wall thickness — Type M copper, with its thinner walls, develops through-wall leaks faster than Type L or K once pitting starts
- Water hardness — harder water accelerates internal scaling and pitting
- High water velocity — undersized pipe or high pressure can accelerate erosion at bends and fittings
None of this means your specific pipes are guaranteed to fail — plenty of original copper systems perform fine for decades. But if you’re seeing recurring pinhole leaks in different spots, these are the underlying factors worth understanding before deciding between repeated spot repairs and a full reroute.