A fine spray, a steady drip, or a green-blue crusty stain on a copper pipe usually means a pinhole leak, a tiny hole eaten through the pipe wall from the inside out. They are sneaky: the hole is small, but the cause is corrosion that is often happening up and down the whole line, so a pinhole is frequently the first of several. Here is how to stop the water now, make a repair that lasts, and figure out whether one patch is enough or your copper is on borrowed time. For the broader emergency steps, pair this with how to stop a leaking pipe.
If a pipe leak turns into a burst, it becomes an after-hours emergency fast — see what an emergency plumber costs and which leaks can wait.
What Causes Pinhole Leaks in Copper
Pinholes come from corrosion attacking the copper from the water side. The usual drivers are aggressive water chemistry (low pH, high chlorine or chloramine, or high mineral content), water velocity that is too high from undersized pipe or excessive pressure, and stray electrical grounding through the plumbing. The important takeaway: if your water or your install conditions caused one pinhole, the same conditions are working on the rest of the pipe. One leak is a data point, not necessarily a one-off.
Step 1: Stop the Water and Dry the Spot
Shut off the water (the nearest valve or the main), open a low faucet to drain the line, and dry the pipe completely, no patch sticks to a wet pipe. Sand the area around the pinhole bright with emery cloth so any temporary fix bonds.
Step 2: The Temporary Fix (Buys You Days)
A temporary patch gets you to the weekend or to the plumber, it is not a permanent repair. Options, best first:
- Pipe repair clamp / sleeve clamp. A repair clamp with a rubber gasket bolts over the pinhole and seals it solidly, the best stopgap.
- Epoxy putty. Plumbers epoxy putty kneaded and pressed over a dry, sanded pinhole holds low-pressure leaks for a while.
- Self-fusing silicone tape. Stretched tightly over the spot, fine for a tiny weep until you can do it right.
Step 3: The Permanent Repair
The real fix is to cut out the bad section and splice in new pipe. You have two routes:
- Solder in a copper coupling. Cut out the pinholed inch, clean and flux the ends, and sweat in a new piece with couplings. Strongest, cheapest in parts, needs a torch and some skill.
- Push-to-connect (SharkBite) repair. Cut out the bad section and join new pipe with push-to-connect fittings, no torch, no flame near framing. Our SharkBite vs. soldered breakdown covers when each makes sense.
One Pinhole or Time to Repipe?
This is the judgment call. A single pinhole on an otherwise healthy line, patch and move on. But if you are getting repeated pinholes in different spots, or the pipe is thin and green all over, the corrosion is systemic, and you are better off planning a repipe (often in PEX, which does not pinhole) than chasing leaks one at a time. Compare the running cost of repairs against the cost of the burst pipe that a missed pinhole eventually becomes.
When to Call a Pro
Temporary clamps and putty are DIY. Call a plumber for the permanent repair if you are not comfortable soldering or working in a tight wall cavity, if the leak is inside a wall or ceiling (water tracking can hide real damage), or if you are seeing repeat pinholes, that one needs a water-chemistry and pressure assessment, not just another patch.
Frequently Asked Questions
What causes pinhole leaks in copper pipes?
Pinholes are corrosion eating through the pipe from the water side out. The common drivers are aggressive water chemistry (low pH, high chlorine or chloramine, hard or mineral-heavy water), water moving too fast through undersized pipe or at high pressure, and stray electrical current grounded through the plumbing. Because the cause acts on the whole line, a single pinhole is often the first of several rather than an isolated defect.
Can you fix a pinhole leak without replacing the pipe?
Temporarily, yes, a repair clamp, epoxy putty, or self-fusing tape over a dry, sanded pinhole will hold for days to weeks. But those are stopgaps. The permanent fix is to cut out the corroded section and splice in new pipe, either by soldering in a copper coupling or using push-to-connect fittings. If you are getting repeated pinholes, patching is a losing game and repiping is the real answer.
Is a pinhole leak in copper serious?
The leak itself may be small, but yes, take it seriously. The hole means corrosion is active in your copper, so more leaks are likely, and a slow pinhole inside a wall or ceiling can cause hidden water damage and mold long before you see a puddle. Stop the water, patch it, and decide whether you are dealing with a one-off or systemic corrosion that calls for a repipe.
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