Why copper pipes get pinhole leaks in Southwest Florida

Copper was the good pipe. It went into most Southwest Florida homes built from the 1960s into the 1980s, and a well-installed copper system in gentle water can last fifty years. Ours is not gentle water, and a lot of that copper was laid in sand under the slab. The result is a call we get often on older homes: a tiny leak, the size of a pin, that appeared out of nowhere in a pipe that looked perfect.

What a pinhole leak is

A pinhole is pitting corrosion. Instead of the whole pipe thinning evenly, the water attacks one spot on the inside wall and digs a small crater. The crater deepens until it breaks through, and the first sign is a bead of water, a fine spray, or a green-blue stain where the pipe is exposed. Behind drywall or under the slab, the first sign is a damp patch, a smell, or a water bill.

The leak is small. The problem is not the leak. The problem is that a pit that broke through in one spot has siblings all along the same pipe, at different depths, all growing.

Why it happens here

• Water chemistry. Utilities in Lee and Collier County treat with chlorine or chloramine to keep the water safe. Both are oxidizers, and over decades they attack the protective film that copper builds on its inside wall. Where the film breaks, a pit starts. Water on the hard side and warm water out of the ground both push the reaction along.
• Velocity. Water moving too fast through copper scours the inside of the pipe, especially at elbows and on the hot side. Undersized lines, a recirculation pump, or high utility pressure all raise velocity.
• Poor installs and flux. Acid flux left inside a joint keeps eating the pipe for years. So does a joint that was overheated, or a fitting with a burr that creates turbulence. A leak at every elbow on one run is a sign of the original installer, not the water.
• Soft copper in the slab. Under the floor, copper tubing sits in damp fill, sometimes with salt in it, and in contact with the concrete. The outside of the pipe corrodes at the same time as the inside. Every spot where the tube rubs the slab as hot water expands it wears a little thinner.
• Salt air. On Fort Myers Beach, Sanibel, and the islands, exposed copper in garages and at the water heater pits from the outside too.

None of this is a defect in the house. It is what copper does in this water over forty or fifty years.

One leak means more are coming

This is the part homeowners do not want to hear, and the part that matters most. Pitting is not a single event. The same water ran through every foot of copper in the house for the same number of years, so when one spot breaks through, the others are close behind. The pattern is a first pinhole, then another some months later in a different room, then two more, each one behind a different section of drywall or under a different tile.

Repairing each one is the right emergency response and the wrong plan. Every repair is a cut, a coupling, and a patch, and the pipe on each side of the coupling is the pipe that was already failing.

Patch or repipe

• Patch when it is the first leak, the pipe is accessible, the copper is under thirty years old, or you need time to plan. A licensed plumber cuts out the section and splices in new pipe or PEX with proper fittings. A clamp or epoxy is a stopgap, not a fix.
• Repipe when it is the second leak, the copper is original to a 1960s to 1980s house, the leak is under the slab, or the copper shows green crust at several joints. The tipping point is usually the second leak, because that is when it becomes clear the first was not a fluke.

The homeowner’s part is turning the water off, clamping the drip if the pipe is exposed, and photographing what you found. Soldering a repair on old, thin copper is where DIY stops: the wall is too thin to take heat well, and a joint that fails inside a wall is a worse leak than the pinhole was.

A repipe replaces every supply line in the house. On a slab home here, the old copper under the floor is abandoned where it lies and the new lines run through the attic and down the walls, which means no jackhammer and no disturbed flooring. Small drywall openings at each fixture are patched afterward. The work is permitted, pressure tested, and inspected.

What replaces failing copper

PEX is cross-linked polyethylene, a flexible plastic pipe that does not corrode, does not react with chlorine or chloramine, does not scale like copper in hard water, and runs from a manifold or a trunk line to each fixture in a single pull with very few joints. It handles the heat of a Florida attic, and it takes a small amount of expansion without stress. It is the usual choice for the long attic runs in a repipe here. CPVC and new copper are still used where they fit best, and a repipe often combines them: PEX for the runs, copper at the water heater and where a rigid line is wanted, CPVC where it matches existing work. The right combination depends on the house.

New copper is still a fine pipe, but new copper in the same water with the same chemistry starts the same clock over again.

Water treatment helps, but it does not undo

A whole-home filtration system that removes chlorine and chloramine before the water reaches your pipes takes away the main driver of pitting. On copper that is still in good shape, that is a real way to extend its life. On copper that is already leaking, it slows the next pit but cannot put metal back on a wall that has been eaten away. If you repipe, treatment protects the new system and everything downstream of it, including the water heater and the fixtures.

If you have found a pinhole, take a photo of the pipe, the leak, and any green or white crust nearby, and note whether it is the first. Send it to us and we will tell you whether it looks like a patch or the start of a pattern.