Pinhole leaks in copper pipe

How copper gets a pinhole

Copper wears from the inside. Water chemistry, high velocity at a tight elbow, burrs left from cutting the pipe years ago, or flux that was never flushed out can all eat a pit into the wall of the tube. When the pit goes through, you get a pinhole: a hair-thin jet or a slow bead that grows a crusty green-blue bloom on the outer wall of the tube.

Where we find them

• Hot-water lines near the water heater, where the water is warmest and fastest.
• The first elbow after a pump or a pressure-reducing valve.
• Horizontal runs over the basement ceiling, under the insulation.
• Copper that touches steel ducts or hangers without an isolator.

The repair

1. Shut the main and drain the line at the lowest tap.
2. Cut out at least a few inches either side of the hole so the new joints land on sound pipe.
3. Look inside the cut piece. Pitting along the bore tells us whether the rest of the run is going the same way.
4. Join in new copper with soldered or pressed couplings, or PEX with transition fittings where access is tight.
5. Restore pressure, watch the water meter dial for movement, and recheck after a day of use.

Planning ahead

A single pinhole is a repair. A pattern is a budget conversation. Our repiping page covers how we replace copper runs in finished basements with the least drywall opened, and leak detection covers how we find leaks you cannot see yet.