Choosing the Right Plumbing Material: Age, Water Chemistry, and System Longevity

Plumbing contractors with knowledge of how materials age and perform under different water conditions can better differentiate between systemic and isolated issues and help their customers avoid both unnecessary costs and the frustration and damage of repeated piping failures. 

Chronological Versus Service Age

Different materials age differently, and their aging is often impacted by local water conditions. When evaluating how much of a system to replace, the chronological age of the pipe is a contributing factor, but you don’t necessarily need to replace pipe just because it is old or ignore potentially systemic issues because the pipe is within its expected service life. Local water conditions can accelerate aging in some materials and there are visible signs that can be early indicators of the need for replacement.

Copper: Copper piping will show signs of corrosion in the form of discoloration or a general thinning over significant lengths, which may be visible during repairs. You may also notice greening on the outside of the pipe, which is a sign of internal corrosion. If there are extensive patches of green, the pipe may be nearing end of life. If signs of corrosion are small and isolated, potential failures may be limited to specific sections of pipe, such as those touching other metal. However, if the municipality has switched to chloramines for residual disinfection, the change could be contributing to accelerated corrosion in copper pipes, which could suggest a repipe is warranted.

PEX: PEX piping is susceptible to premature aging and degradation from drinking water when temperatures exceed 140°F and pressures of 80 PSI+ with an Oxidative Reduction Potential above or below 825 mV. In addition, a recent technical note from the Plastics Pipe Institute highlighted the risk that chlorine dioxide disinfection could increase the likelihood of premature failure in PEX pipes as well as copper, steel, PE-RT, and PP-R piping. While not as common as free chlorine and chloramines, use of chlorine dioxide disinfectant in municipal water systems is growing, increasing over 104% since 2020, according to the US EPA. 

In clear or translucent PEX piping, look for a popcorn-like localized discoloration or subtle bubbling on the surface of the pipe. This is a sign the pipe is experiencing chlorine-based degradation in your drinking water, which can lead to premature failure. If this is widespread, replacing the entire system may be necessary before the leak causes water damage. In red, white or blue-colored PEX piping, the effects of chlorine-based degradation may not be visible until pinhole leaks occur.

CPVC: CPVC piping will change color as it ages, but the discoloration does not indicate reduced performance. CPVC is 100% immune to all known chlorine-based disinfectants in drinking water. The change in color is not an indicator of internal corrosion and CPVC’s pressure-bearing capability actually increases with age. As the material ages, it requires specific, readily available tools to be used when cutting older CPVC pipe. However, it will continue to provide reliable service, with proper installation

When Age Isn’t the Issue

Of course, not all failures are “age” related. All plumbing materials can be weakened by exposure to certain chemicals. In most cases, these issues occur when incompatible materials come into contact with the exterior of the pipe. These failures will typically be isolated to the area of exposure. Less likely are exposures to the inside of the pipe that could occur if the water becomes contaminated with incompatible chemicals, such as those in some solvents, plasticizers or petroleum-based oils. If internal exposure to incompatible chemicals has already caused one failure, it is likely the whole system has been compromised and should be replaced.

Failures due to installation errors are another example of cases that are usually isolated but occasionally require a repipe. With PEX this is often due to fittings that have been improperly seated or crimped. A failure at a fitting could represent an isolated error in an otherwise proper installation or it could be a sign of an inexperienced plumber who repeated the same mistake with every fitting.  

The same concern applies to CPVC pipe installations and the problem of “dry fits.” This occurs when an installer neglects to apply solvent cement to one or more fittings in the system. To reduce the risk of these errors, the 2024 plumbing codes now allow the use of high-contrast green solvent cement, in addition to the traditional yellow cement, making it easier for inspectors to visually confirm that all CPVC joints have been properly welded.

Protecting Against Premature Aging

If a repipe is required, the cause of failure should be considered when choosing a material for the new system, particularly if the issues with the existing system were related to incompatibility with local water conditions. You don’t want to replace a material that has failed prematurely due to the effects of chlorine, chloramines or chlorine dioxide with the same material or a material with similar vulnerabilities. 

As a chlorinated compound, CPVC is impervious to degradation from chlorine, chloramines and chlorine dioxide disinfectants in drinking water, allowing the material to perform reliably in water conditions that accelerate aging in PEX and copper pipes. CPVC is also significantly less expensive than copper, potentially reducing the financial burden of the repipe on homeowners, and may improve water pressure and flow compared to PEX systems due to the pressure drops introduced by PEX insert fittings. 

CPVC’s immunity to chlorinated drinking water helps protect plumbing systems from future changes in water chemistry, which are common as municipalities adapt their treatment practices to growth, changes in the water supply, or new research on the health effects of certain disinfectants.  

For more information on specifying, installing or servicing CPVC, visit www.flowguardgold.com.