Why Plumbers Can’t Ignore Water Compatibility in Material Selection

Potable water treatment in the U.S. is dominated by the use of three chlorine-based disinfectants. Free chlorine is the most commonly used disinfectant, followed by chloramines, which treat the drinking water used by more than 20% of Americans. Chlorine dioxide, the most powerful of the three, has been adopted by 5% of large municipal water systems.

Yet only one residential plumbing material in use today – CPVC – is inherently immune to damage from drinking water treated with these disinfectants. PEX is vulnerable to degradation from chlorine and chloramines and leading PEX manufacturers advise against its use with chlorine dioxide.

If there was ever a must-have feature for a residential building product, the ability of potable water pipes to handle the water flowing through them would be one.  

The Science Behind Water Compatibility 

CPVC stands for chlorinated polyvinyl chloride, and the chlorination process used to produce FlowGuard Gold CPVC provides natural immunity to drinking water treated with chlorine-based disinfectants. Because FlowGuard Gold plumbing systems are chemically compatible with chlorinated drinking water, that immunity persists throughout the life of the material.

PEX is a polyolefin that is inherently susceptible to damage from chlorinated drinking water. PEX manufacturers fortify the material against chlorine by adding antioxidants during the manufacturing process. These antioxidants are consumed by interacting with and deactivating the chlorine in the water. The longer the pipe is in service, the fewer antioxidants remain to combat the effect of chlorine on the pipe.

Plus, there are multiple factors that can accelerate the consumption of the antioxidants and/or lead to accelerated failures in PEX. In Technical Note 53, the Plastics Pipe Institute identifies temperatures above 140° F, pressures above 80 psi, and an oxidation reduction potential (ORP) above 825mV as conditions that can accelerate chlorine degradation in PEX pipes. In addition, exposure to UV light consumes PEX’s chlorine-fighting antioxidants and antioxidants can leach into other products that come in contact with the pipe, such as adhesive tape. 

Real-World Implications of Chlorine Incompatibility in Residential Water Pipes 

Piping systems that are incompatible with chlorinated drinking water present multiple problems for plumbers, builders and homeowners: 

• Premature failure: Water conditions that exceed the ORP threshold defined by the PPI are not uncommon. If you install PEX, you have no way of knowing how local water conditions will affect the pipes and no way to predict the expected lifespan of the plumbing system. In one case we documented, a family began experiencing systemic failures in PEX pipes when their new home was less than ten years old. Repiping specialists report they regularly replace PEX piping in newer homes. 
• Inability to adapt to changing water conditions: Even if PEX pipes can handle local water conditions at installation, there is a high probability those conditions will change as municipalities adapt their treatment practices to changing water conditions. The most significant change is the switch to chlorine dioxide. In Technical Note 67, the PPI notes that chlorine dioxide “has the potential to reduce the service life” of several materials, including PEX piping. As noted previously, several leading PEX manufacturers advise against the use of the material “as part of any potable-water distribution system in buildings where chlorine dioxide is used for secondary disinfection.” The problem is plumbers and builders can’t guarantee the pipes installed today won’t carry water treated with chlorine dioxide in the future. 
• Lack of warranty protection: Because of the uncertainty around the performance of PEX pipes in a particular application, many PEX warranties are voided as soon as chlorinated water flows through the pipe. 
• Increased legal risk: When PEX is incompatible with local water conditions, failures aren’t limited to one home; they can affect an entire development, potentially resulting in class-action lawsuits. There has been at least a dozen settled class-action lawsuits resulting from systemic PEX failures in recent years.   
• Emerging failure modes: In the last several years, a new failure mode was identified for PEX pipes. These failures are caused by the bending of the pipe, as can occur with expansion and contraction, after the pipe has been exposed to chlorinated water. Chlorine degradation appears to weaken the inner wall of the pipe and make it susceptible to cracking when bent. Plumbing expert Roger Wakefield shows how to identify this failure mode in the video at the end of this post. 

The Benefits of Water Compatibility in Residential Plumbing Systems 

By contrast, FlowGuard Gold CPVC’s inherent immunity to damage from chlorinated drinking water delivers a number of benefits. 

• Elimination of a common failure mode: Exposure to chlorine-based disinfectants in drinking water is a common cause of failure in PEX and copper pipes and fittings. Chlorine-based disinfectants in drinking water – including chlorine dioxide - will not damage FlowGuard Gold CPVC pipes and fittings. If the water is safe to drink, it’s safe for FlowGuard Gold CPVC.
• Warranty protection: The FlowGuard Gold CPVC warranty is not voided by exposure to chlorinated drinking water.
• Application flexibility: FlowGuard Gold CPVC’s temperature and pressure ratings are not compromised by chlorinated drinking water, as is the case with PEX. The ability to withstand chlorinated drinking water at temperatures above 140° F and pressures above 80 psi provides the application flexibility engineers, builders, and plumbers need.
• Reduced risk: The FlowGuard Gold warranty explicitly covers chlorinated drinking water, which no other warranty does. Properly installed, maintained and serviced FlowGuard Gold doesn’t experience spontaneous failures. The material has been proven in U.S. water systems for more than 60 years and FlowGuard Gold CPVC has never been the subject of a certified class action lawsuit.
• Future-Proof Plumbing: With FlowGuard Gold CPVC, you don’t have to worry about the impact of future changes to municipal water treatment on the plumbing systems you install today. Even if the municipality where you are working introduces chlorine dioxide treatment in the future, FlowGuard Gold CPVC can handle it. As PPI’s Technical Note 67 states, “chlorine dioxide is not known to be aggressive to CPVC at elevated temperatures of 200°F and below.”   

The Professional Plumber’s Choice

If you want to protect your customers from the risk of premature failure and your business from the risks associated with plumbing systems incompatible with chlorinated drinking water, choose FlowGuard Gold CPVC. It’s the choice of expert plumbers like Roger Wakefield, who explains how chlorine degradation can cause a particular type of PEX failure in this video.