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interior view of pipes WHAT CAUSES PIPES TO LEAK? (pipe failure)

Brown or discolored water, low water flow hot or warm spots in the floor, soaked carpeting, ceilings or walls and abnormally high water bills are all signs of failing pipes.
A number of factors can work alone or in combination to affect the rate of corrosion in any piping system.

Depending on the number and degree of these factors, even a new piping system can show signs of corrosive wear in as few as two years after installation. The problems are most acute in properties that have been in service 15 years or more, however.

The corrosive effect the source water can have on a piping system does not mean water quality is poor, in fact even those areas where the drinking water has been rated among the best in the country.

As an example, in the Pacific Northwest region of the United States and Canada, the source water quality has been rated as some of the best drinking water in the world. Yet, that water still has a very corrosive effect on piping systems because of several factors unrelated to water quality:
  • Water chemistry
  • The pH of the water
  • The amount of oxygen in the water
  • The temperature of the water
  • The velocity/pressure of the water in the pipe
The rate of corrosion can also be affected by the chemical make up of the water and the amount of galvanic corrosion from the use of different metals in or in contact with the piping system.

Let's take a closer look at the most common causes of corrosion of piping systems.

The pH Of The Water
Acidity of a water sample is measured on a pH scale, which ranges from zero (maximum acidity) to 14 (maximum alkalinity). The middle of the scale, 7, represents the neutral point, and acidity increases from neutral toward 0, while alkalinity increases from 7 to 14.

This is all pretty straightforward, except that the pH scale is based on logarithmic progression, much like the commonly used "Richter" scale for earthquake measurement. This means that a difference of one pH unit represents a tenfold change in acidity.

In copper pipe systems, when the pH is more than 8, a copper oxide film usually forms on the pipe walls. This film acts as a barrier that slows the affects of corrosion. However, when the pH in the water supply is lower than 8 the copper oxide film (barrier) is dissolved, which leaves no protective barrier and subjecting the pipe to the corrosive action of the water. The ultimate result? Pinhole leaks that can damage walls, flooring and structural components.

Oxygen and Water Temperature
A domestic water system is an "open" system, in which the water in use is always being replenished with fresh, oxygenated water. Dissolved air in water consists of about 30% oxygen and the rest is mostly non-corrosive nitrogen.

Oxygen, however, degrades metals through an electro-chemical process of internal oxidation. As a result, the metal gradually gets converted to an oxide (rust) and becomes thinner and weaker in the process. As the pipe corrodes, the impurities are deposited in the water lines and encrusted build up is the direct result of this oxidation process.

As for water temperature, the higher the water temperature, the faster the rate at which this oxidation occurs. While oxygen content decreases under higher water temperature pressure, these higher temperatures and pressure conditions can actually accelerate the oxidation process. Experience shows that corrosion is more pronounced in hot water lines than in cold water lines.

Water Velocity
Water velocity problems are usually associated with a "closed loop" piping system in which it's necessary to pump or circulate the water.

Erosion corrosion occurs at locations where water turbulence develops, usually caused by excessive velocity. This is typically encountered when water makes sudden changes in direction (such as sharp pipe turns and elbows) and through "flow" obstacles such as burrs and excess solder from improperly soldered joints.

Other major contributing factors to this type of erosion corrosion include oversized circulation pumps, installation of undersized distribution lines and an improperly balanced system.

Repair Options
Currently, homeowners have several options from which to choose. However, none of the options address the root cause of the problem; they simply try to correct the symptoms. Most of the options are also costly. These options include:
  • Fixing the leak by application of external solder
  • Replacing a small or larger section of tube
  • Re-plumbing the entire house
    (However, even a complete re-plumb with new copper tubing does not guarantee that the problem will not recur after a period of time.)
  • Re-plumbing and replacing copper with PVC or CPVC
  • Coat the inside of existing pipes with epoxy
  • Purchasing potential cures (of questionable value), such as magnets
The cause and effect of the corrosion must first be identified so the appropriate repair is made. In almost every case, using one or more traditional repair methods involves tearing out walls and pipes and repairing or replacing them. Plus, in the case of chemical flushing, powerful chemical agents must be used.

These traditional methods of repair are expensive in their own right - but they're even more costly because of the amount of associated "civil work" that must be done (i.e., wall, tile and ceiling repair that is needed after accessing pipes behind walls and ceilings.)

These more traditional methods of repairing the piping system usually result in closing entire sections of buildings for extended periods. In revenue-generating properties such as hotels and motels, rooms not available for use result in a direct revenue loss, not to mention the inconvenience to staff and guests in other areas of the facility.

And, after all of the painful and costly experience of making repairs, unless the causes of corrosion have been properly identified and corrected, corrosion of the system starts again as soon as the water is turned back on.

See also:
Copper Pipe Failure
Galvanized Pipe Failure