While the exact cause of copper tube corrosion is unknown, nobody can doubt its existence. Copper tubes corrode from the inside out. The interior of the tube forms copper salts that are soluble in water, and water running through the tube carries these copper salts away, slowly eating away at the tube. Once the tube has deteriorated, water starts to slowly leak from tiny holes left behind; these are referred to as pinhole leaks. There are a few things that are definite contributors to copper tube corrosion. Here's what they are and how to prevent them.
Stray Current Corrosion
When direct current flows through a copper tube, it accelerates the formation of copper salts and the erosion of the tube walls. This is known as stray current corrosion. It's typically seen in water mains near a large electrical ground – the direct current is attracted to the nearest conductor, which is the copper pipe in the soil. However, this type of corrosion isn't limited to water mains; any copper tubes near a ground may pick up stray direct current and begin to corrode.
To check for this type of corrosion, have a licensed electrician check for electricity flowing through the copper tubes using a direct current voltmeter. Even a very small amount of current can cause copper salts to form in the walls of the tube. If your copper tubing does have current flowing through it, an electrician can install dielectric couplings on the tubing to isolate it from the source of the current. You can also sheathe the entire tubing in plastic piping or wrap it in electrical tape to prevent stray current from coursing through the tube.
The formation of copper salts is exacerbated by hard water. The dissolved minerals in hard water cause it to become alkaline – both acids and bases will slowly corrode copper tubing, although it's rare to encounter water with significant acidity. Over time, the alkaline water will corrode the inside of your tubes and slowly erode through them.
You can prevent alkaline water from corroding your tubing by installing a water softener near your water source. The water should be softened before it ever encounters your copper tubing.
Municipal Water System Additives
If your copper tubing is using water from the municipal water system, this can contribute to corrosion and pinhole leaks. Many cities add chloramine to their water supply in order to kill bacteria. Chloramine is a mixture of chlorine and ammonia that lasts longer in the municipal water supply than chlorine alone. Unfortunately, chloraminated water has been implicated in rapidly causing corrosion in copper pipes.
Carbon filtration will remove chloramine from water. Installing a filtration system with a carbon filter at your water source may help prevent pinhole leaks in your copper tubes.
By eliminating the risk factors of corrosion, you can preserve the integrity of your copper tubes and help prevent pinhole leaks. Filter and soften your water before it enters into your tubing, and have an electrician check your copper tubes for stray direct current and isolate them if necessary. If your tubes begin to experience pinhole leaks, it's likely that you'll have to replace all of them at once – corrosion attacks the whole system equally, and experiencing a few pinhole leaks usually means that more are on the way.