What a pinhole leak is
A pinhole leak is a tiny opening that forms where the copper wall has thinned from pitting corrosion. Underground, it may release only a fine stream, which soaks into the soil instead of surfacing. The first clue is often a meter that never quite stops, or one patch of lawn that stays green through a dry month.
Pitting can start on the inside of the pipe from water chemistry, or on the outside where the copper touches certain soils, debris or other metals. Fullerton's water is hard, a blend of local groundwater and imported supply, and mineral content is one of several factors that can influence how copper ages. No single cause applies to every home.
Common contributors to copper line pitting
| Factor | Where it acts | What it can lead to |
|---|---|---|
| Water chemistry and minerals | Inside the pipe | Pitting that thins the wall from within |
| Aggressive or wet soil | Outside the pipe | External corrosion along buried sections |
| Contact with other metals | At fittings or crossings | Corrosion where dissimilar metals meet |
| Rocks or debris against the pipe | Outside the pipe | Abrasion and stress points |
| Thin-wall tubing underground | Whole run | Less material to lose before a leak opens |
Signs a copper line has pinholed
Fix the pinhole or replace the line?
- IfOne pinhole, and the exposed pipe looks clean and solidThenA section repair is often reasonable.
- IfThe plumber finds thin or pitted pipe around the leakThenMore leaks are likely nearby; ask about replacing the run.
- IfThe line has already had a pinhole repaired beforeThenRepeated pinholes usually point toward replacement.
- IfThe line runs under a driveway or hardscapeThenAsk whether rerouting or a trenchless method avoids repeated digging there.
Questions to ask about a copper line leak
- Where exactly is the pinhole, and how was it located?
- Does the pipe on either side of the leak look sound?
- What type of copper is in the ground now, and what would you use for a repair?
- If I replace the line later, will this repair be wasted work?
- Should anything else, such as a pressure regulator, be checked at the same time?
Common questions
Does hard water cause copper pinhole leaks?
Water chemistry is one possible factor, along with soil conditions, installation details and the pipe itself. Hard water alone does not explain every case.
Can I patch a pinhole myself?
A buried service line requires digging, shutting off water and making a sound pressurized joint. That work is best left to a licensed plumber.
Is it worth replacing copper with copper?
Sometimes. Copper rated for underground use is still common. Your plumber may also suggest PEX or polyethylene depending on the route and method.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.