All water naturally absorbs gases like oxygen and carbon dioxide. To see this effect, fill a clear glass with tap water. Let the glass sit overnight. The next morning, notice small air bubbles formed on the walls of the glass. This is the dissolved gases separating out of the water. All corrosion is a complex chemical process involving oxygen. Rust is called iron oxide. Green copper corrosion is called cupric oxide. The key word is "oxide," which means oxygen. Oxygen combines with the metal, forming corrosion. The matter is complicated further by carbon dioxide, which is an acidic gas.
The "Hard Water Organization" identified several dissolved minerals in water. Water with minerals is referred to as "hard water." Some of the minerals include calcium, hydrogen sulfide (sulfur) and magnesium. Furthermore, municipalities add fluoride to the water, to help prevent tooth decay. These minerals are not harmless to metal. They are all alkaline or acidic and corrode metal pipes.
The end effect is all the same: Pipes and fixtures are corroded from the inside out. The ingredients dissolve the metal, making the walls thin. Pinhole leaks develop when a mineral eats all the way through a pipe. If the pipe is inside a wall, a slow drip will go undetected. The moisture, however, will lead to black mold growth and rot. Other times, the pipe walls become so thin an eventual blowout is inevitable. When this happens to a water main, crews usually have to dig up the main and replace the bad section.
Laurie S. McNeill and Marc Edwards of the Virginia Technological University and experts at the Clean Water Store concur on some common solutions. First, chemicals such as orthophosphates coat the inside of pipes, preventing scale buildup. Also, calcium neutralizing filters are installed in the piping system to counteract calcium. Finally, various home and commercial softening systems exist to remove minerals.