The number people quote
InterNACHI's life expectancy chart lists copper water lines at about 70 years (InterNACHI). For comparison, the same chart lists PEX at about 40. Those are averages for planning, not a countdown. Plenty of copper outlasts that, and some fails much sooner.
What makes copper fail early
- Water chemistry: Acidic or aggressive water slowly eats the pipe wall from the inside, and pinhole leaks follow. Private wells are more prone to this than treated city water.
- High velocity: Undersized pipe, a recirculating pump running too fast, or high house pressure wears the inside of elbows and tees.
- Thin-wall pipe: Type M copper has a thinner wall than Type L and gives less margin.
- Installation: Too much flux or poorly made joints can corrode in the years after the install.
- Contact with other metals: Copper joined directly to galvanized steel without a dielectric fitting corrodes at the joint.
Signs your copper is near the end
- A second or third pinhole leak in a few years
- Green or blue staining at joints and fittings
- Blue-green stains in sinks and tubs
- Small leaks showing up in different parts of the house, not one spot
Repair or repipe?
One pinhole is a repair. Repeated pinholes in different places means the whole system is thinning, and patching becomes a cycle of leaks and water damage. That is when a repipe usually costs less over time than fixing leak after leak. If you are not sure what is in your walls, start with galvanized, copper, or PEX.