Pinhole leaks in copper water lines
A pinhole leak in copper supply pipe sprays a fine mist or leaves a green spot.
Updated · 3 min read
If you read one thing
Pinhole leaks are tiny holes worn through copper pipe from the inside. One can be patched with a short section of new pipe. Repeated pinholes in different spots mean the copper is wearing out and a repipe is the lasting answer.
In this guide
What a pinhole looks like
A fresh pinhole sprays a fine stream or mist. Older ones seep and leave green or blue crust on the pipe and white mineral trails beside it.
In Alhambra's hard water, around 240 ppm per the city water report, slow seeps often build a crust that marks the leak.
Why copper wears through
Common factors include water chemistry, high water velocity from undersized pipe, sharp turns after fittings, and stray electrical current on the pipes.
Hard water alone usually forms a protective scale, so pinholes in hard-water cities often trace to velocity, workmanship or pipe age instead.
Repairing a single pinhole
The water is shut off, the damaged section cut out, and new pipe soldered or joined with press fittings. Clamps are a temporary fix, not a permanent repair.
Drywall is opened only as far as needed, and the area is dried before closing.
When to plan a repipe
About 77 percent of Alhambra homes were built before 1980, per the city's housing needs report. Copper from that period has decades of wear.
If you have had two or three pinholes in a short time, the rest of the pipe is likely similar. A repipe in copper or PEX replaces it all.
Alhambra homeowner questions
Can epoxy pipe lining fix pinholes?
Lining can coat the inside of pipe, but it depends on pipe condition and access. We discuss options case by case.
Do pinholes mean my water is unsafe?
No. They reflect pipe wear, not water quality.
Why does my pinhole leak only on the hot line?
Hot water moves faster in recirculating systems and is more aggressive to copper, so hot lines often fail first.