What causes a pinhole leak in a copper water pipe?

Posted on by Andrew LeVahn

LeVahn Bros. Plumbing &

Hardware Hank Maple Grove, MN

WHAT IS A PIN HOLE WATER LEAK

A pinhole leak is a small hole that develops in a pipe causing a mist or stream of water to shoot out. In most cases these leaks develop due to the pipe being eroded from the inside out. There are a number of factors as to why a leak happens. Some of the main factors that lead to a leak include: age, your municipalities water pressure, the amount of minerals found in your municipalities water, how the pipes are configured(i.e. elbows, bends, turns etc.), what season it is, and how the plumbing was installed.

pinhole leak in a copper pipe

Pinhole leak in copper pipe

WHAT CAUSES A PIN HOLE WATER LEAK

In most cases the leaks occur near the water main inside the house. They occur near the water main because this is where the water pressure is the greatest in the home. Just like how water over time can cut deep into rock creating things like the Grand Canyon it also can erode the inside of your pipe. It slowly erodes the inside of the pipe until it eventually breaks through. This meter horn developed a leak at the bend on the left side. When a meter horn leaks you should check with your municipality to see if they are responsible for replacement, or if it’s up to you. In this case the resident was responsible for replacement so they came in and purchased one from us and installed it themselves.

pinhole leak in a meter horn

Meter Horn with a pinhole leak

Most of the factors that cause pinhole leaks can’t be avoided. We can’t change the mineral content or temperature of the water coming into the home. Most leaks occur at or near a joint. In other words where a connection is. This could be an elbow or even a coupling. When water passes by a joint there is turbulence. The water swirls and spins as it passes through the joint. Preventing this is somewhat unavoidable. The turbulence causes the water to erode the pipe from the inside out.

copper pipe erosion

copper fitting erosion

When a leak occurs at a joint it may be due to the installer failing to ream out the copper after cutting it.  When a copper pipe is cut with a pipe cutter it gets pinched as it’s being cut. This creates a lip on the inside of the pipe. This lip can exaggerate the amount of turbulence that occurs at the joint. The pipe in the picture below has multiple holes that probably occurred due to  the installer not reaming out the pipe after cutting it.

pinhole leak at the joint

Pinhole leaks at solder joint

To help avoid this from occurring you should always use a pipe reaming tool to get rid of the edge that’s created when a pipe is cut. Some pipe cutting tools have a reamer attached right to them. If your pipe cutter doesn’t have a reamer, or if you don’t like that style, you can use a different style such as the one below. It is a very simple tool to use. All you need to do is run it along the inside edge of the pipe you cut and it takes off the lip created when the pipe was cut.

copper tubing reaming tool

Copper tubing reaming tool

PIN HOLE PIPE LEAKS IN MINNESOTA

In Maple Grove and Plymouth Minnesota (the cities near where our store is located) there is high water pressure with lots of minerals in the water. These factors coupled with the average age of the homes (around 20-30 years old) means that we’ve had a large volume of pinhole leak calls in recent years. High mineral content in the water can cause multiple plumbing issues. Everything from water heaters to faucets and pipes are affected by the minerals. Softening your water doesn’t help much either. Softening water doesn’t remove many of the minerals that are present in the water.

WHAT TO DO FOR A PIN HOLE WATER LEAK

If you get a pinhole leak what should you do? First you need to cut back the copper piping to a point where the copper is still sound. Remember that the pipe has been corroding from the inside out. The spot where the pin hole occurred is just the first place that it broke through. If you were to replace just the small section of piping where the pinhole is located you would probably be repairing another spot six months down the road.

pinhole leak

Paper thin copper removed from a home in Maple Grove

Next you need to replace all the pipe and fittings that you’ve removed. I would recommend replacing the piping with a thicker commercial grade copper. Type “M”copper is the standard grade copper used for residential plumbing. Use a type “L” commercial grade copper instead. It costs a little more per foot but  it’s worth the investment. Make sure you ream out your cuts like mentioned above and solder everything back together.  If you don’t feel comfortable soldering a pipe and you’re going to have someone else do it make sure they cut enough of the bad pipe out and that they use type “L” copper when they replace it (you can also tell if it’s type “L” copper if the writing on it is blue, type “M” is red).

type M and type L copper pipe

Type “M” (red) and type “L” (blue) copper

For more info on pipe leaks check out this blog: copper pipe leak

If you have any questions call us at 763-551-8990

Stop in and see us at 12700 Bass Lake Rd. Maple Grove, MN 55369

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About Andrew LeVahn

I am the fourth generation of LeVahn's. I have been working at LeVahn Bros. since 1994. I went to Minnehaha Academy for high school and Bethel University for college. View all posts by Andrew LeVahn → This entry was posted in DIY, pinhole leak, Pipe Leak, Plumbing and tagged , , , , , , , , , , . Bookmark the permalink.

4 Responses to What causes a pinhole leak in a copper water pipe?

  1. Michael says:

    Hey there. What a great and varied explanation of the ways copper pipe can degrade. Thanks for the info – great pictures. Boiling Water Tap Team

  2. Perfect tip!! I had this problem once and I had to call a professional to get rid of it, now I will handle this issue myself!

  3. Great post! Reading expert advices and ideas can really help you understand why these things have been causing problem in your line.

  4. Really great post! The pictures and information where super helpful in learning about copper piping. Thank you for sharing!!

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