Another green crust on a joint, another stain on the ceiling, another plumber visit. Recurring copper pinhole leaks come from pitting corrosion that slowly eats through the pipe wall, and the pitting can start from water chemistry, high flow velocity, workmanship such as excess flux or burrs, stray electrical current, or a mix. No single cause fits every house. Fullbore Dallas Repiping replaces copper and other water supply lines in Dallas homes through copper repiping, PEX repipes and partial scopes.
When pinholes keep coming, the pattern matters more than any one leak. Where they appear, on which line and how fast they repeat narrows the cause and the right fix.
What a pinhole actually is
A pinhole leak is a tiny hole through the wall of copper pipe, usually from pitting that started on the inside surface. The pit grows outward over months or years until it breaks through. You may see a green or white crust, a fine spray, or a slow drip that shows up as a stain or mold before anyone finds the hole.
Because pitting starts inside, the outside can look fine. A cut-out section shows the inner surface, which tells us much more than the outside does. Pipe with several pits close together is wearing out; one isolated pit may not mean much.
Why copper starts pitting
Several things can start or speed pitting: water chemistry, including the disinfectant and pH; high flow velocity, especially in hot lines and recirculation loops; workmanship such as excess flux, burrs left inside cut pipe or overheated joints; and stray electrical current from a bad ground or bonding fault. Often more than one is at work.
Water chemistry
Dallas Water Utilities treats surface water with chloramine and corrosion control. A December 2023 City memo reports hardness of 120 to 155 mg/L as calcium carbonate. Hardness builds scale in heaters and aerators, but it is not an established cause of pinholes. Studies of how disinfectant chemistry and pH affect copper reach results that depend on the specific water, which is why the utility’s treatment alone can’t be blamed for one house’s leaks.
Velocity and turbulence
Water moving too fast, especially hot water, can wear away the protective layer inside copper. This erosion corrosion shows up just past elbows, tees and fittings where the flow turns. An oversized recirculation pump or undersized pipe pushes velocity up, which is why hot lines on a recirculating system often go first.
Workmanship
Excess flux left inside a joint can keep corroding the pipe for years. Burrs left when pipe was cut, or joints overheated during soldering, make turbulence or weak spots. Leaks clustered near fittings, especially on pipe installed or repaired at the same time, point toward workmanship.
Stray electrical current
Copper water pipe was often used as an electrical ground. A faulty ground, a bonding problem or an appliance fault can push current through the pipe and speed up corrosion. If your pinholes cluster in one area or near the electrical service, have an electrician check grounding and bonding.
What your leak pattern is telling you
Pinholes on hot lines only, near a recirculating loop or just past fittings, suggest velocity. Leaks bunched in one area, or near joints from one round of work, suggest workmanship or a local cause. Pinholes scattered across hot and cold, in pipe of the same age, suggest the system is wearing out together and a broader scope makes sense.
| Pattern | Possible cause | Likely scope |
|---|---|---|
| Hot lines only, near recirculation pump | Velocity, erosion corrosion | Address the pump and sizing; consider hot water line replacement |
| Near fittings from one remodel | Flux, burrs, overheated joints | Repair or replace that section; consider a partial repipe |
| One area near electrical service | Stray current | Electrician checks grounding and bonding; repair the section |
| Hot and cold, all over the house | System-wide pitting | Consider a whole-house repipe |
Keep a simple record: date, room, hot or cold, and what was found at each repair. That record is the most useful thing you can hand us on the first visit.
Pinholes keep turning up in your copper?
We start with your leak history and a look at the pipe, and your written estimate says what a repair or repipe would leave in place.
Is a pinhole an emergency?
A spraying or dripping pinhole means shut the water off and get it repaired now, because even a small leak inside a wall or slab can cause mold and structural damage. A history of pinholes with nothing leaking today isn’t an emergency, but each new one risks hidden damage. Plan your next step before the next leak picks it for you.
In a slab house, a pinhole in an under-slab line can show up as a warm spot on the floor, a meter that moves with everything off, or the sound of running water. Slab leak rerouting moves that line overhead instead of breaking concrete.
Repair, reroute or repipe?
One pinhole on pipe that looks good inside is a repair. Several on one line or area may justify replacing that section. Repeated pinholes across the house, especially once more than one wall or ceiling has been opened, usually point to a repipe. Our guide to repair or repipe walks through the decision.
If you repipe, the material follows from the cause. A properly sized and installed copper system can avoid velocity and workmanship problems; PEX isn’t subject to copper pitting. Our PEX vs copper guide compares the two, and the Dallas repiping cost guide gives our typical ranges and what drives them.
Bring the evidence
Bring your leak record and any cut sections of pipe you’ve kept. On the first visit we tell you which pattern your house shows, what we know and what is still a guess, and what each option replaces. Get an estimate to start, or use the repiping assessment tool to sort your symptoms first.