What a pinhole leak actually is
A pinhole is a corrosion pit that eventually penetrates the pipe wall. It starts on the inside, where water, minerals and flow act on the metal, and it can take years to break through. By the time water is detected, the surrounding pipe has often been wearing for a long time, which is why one pinhole is rarely the end of the story.
No single cause explains every pinhole, and anyone who gives you one confident answer is simplifying. Industry and research sources point to a handful of contributing factors that tend to appear together.
Common contributors
Water chemistry
Dissolved minerals, chlorine and acidity affect how copper reacts. Water that is hard to the taste is not necessarily hard on pipe, but chemistry is the first suspect for pitting.
High pressure
Plumbing codes commonly treat static pressure above about 80 psi as too high. Constant stress strains joints and fittings even when no leak is visible.
Fast-moving water
High flow speed, and hot water pushed by a recirculation pump, can erode the inside of the pipe, especially at bends and fittings.
Heat and installation
Hot lines wear faster. Poor soldering, leftover flux and pipe that rubs against concrete or other metals can start a failure at one spot.
In many Mesa homes the supply lines are thin-walled copper installed decades ago, running through concrete, which makes the combination of age, chemistry and contact worth examining.
A pressure check you can do yourself
- Buy a hose-bib pressure gauge.It is a small, inexpensive fitting that screws onto an outdoor spigot.
- Turn everything else off.Close all taps and make sure no appliance is drawing water.
- Open the spigot and read the gauge.That is your static pressure.
- Check it a few times.Overnight or early morning, water pressure is often at its highest.
If the reading is regularly above about 80 psi, mention it to a plumber. A pressure-reducing valve may be missing or failing, and bringing the number down is often cheap protection for every pipe, fixture and appliance in the house. Pressure that climbs when no one is using water can also point to a thermal expansion issue at the water heater, which the same visit can address.
Signs your pipe may be wearing as a whole
- A second pinhole leak within a few years of the first, anywhere in the house.
- Green or blue crusty deposits at joints, or pitting visible on pipe exposed during a repair.
- Blue-green stains in sinks, which can indicate copper corrosion by-products in the water.
- Frequent small repairs by different plumbers on the same line.
Patch, line or replace?
The right path depends on how widespread the wear is, which is why detection and pressure testing matter. A single isolated pinhole in otherwise healthy pipe is a normal candidate for spot repair. When the pipe has several weak points, the choice usually becomes epoxy lining if it remains sound enough, or repiping if it does not. If the leak sits where the floor is costly to open, rerouting avoids the slab altogether.
Whatever is chosen, address the conditions that damaged the old pipe, or the new pipe inherits them. That can mean setting pressure to a sensible level, insulating hot lines, checking that the water heater is set sensibly and keeping dissimilar metals from touching.
What to tell a technician
The more precise you are, the better the answer. Note when you first noticed the leak, whether it was hot or cold, your pressure readings, whether you have a recirculation pump and any history of repairs. If you can, tell the technician what the exposed pipe looked like during the last repair. For comparing the choices side by side, use our repair, reroute, repipe or line guide.
If you suspect pinholes, our Mesa pipe specialists can test the system and explain what they find, and the SlabGuard Pros homepage lists every way to reach them.
Questions people ask
Is Mesa water bad for copper pipes?
There is no simple yes or no. Water chemistry is one of several factors, and local conditions vary by neighborhood. Your water provider publishes quality reports, and a plumber can interpret them for your home.
Can a water softener cause pinholes?
Softened water can behave differently with metal, and the effect depends on the system and the water. If you recently added a softener and pinholes followed, mention it to your plumber.
Does a pinhole always mean the whole system is failing?
No. An isolated pinhole in healthy pipe can be a one-time event. A pattern of leaks is what points to wear throughout.
Is epoxy lining a permanent fix for pinholes?
It can seal small pinholes and protect the interior of a sound pipe, but it is not right for every line. See our lining page for the limitations and the questions to ask.
Last updated October 16, 2026. This page offers general information to help you understand and describe a problem; it is not a diagnosis of your home. Only an on-site inspection can confirm a leak or the right repair.