Late last year, the Plastics Pipe Institute (PPI) called attention to an important topic with the release of Technical Note 67: Chlorine Dioxide and Plastic Hot- and Cold-Water Plumbing Distribution Pipes. In this note, the PPI analyzes published research on the effect of chlorine dioxide on various piping materials and provides information every plumbing contractor should know.
Why Chlorine Dioxide Is Becoming More Important
Chlorine and chloramines are the most popular disinfectants used by US municipalities to keep drinking water safe. However, in recent years questions have been raised about the disinfectant byproducts (DBPs) that form when bacteria in drinking water interact with chlorine and chloramines in water disinfection. The US EPA, CDC, and independent researchers have published information related to potential health risks associated with these byproducts, leading some municipalities to explore alternative disinfectants.
Chlorine dioxide is an EPA-approved water disinfectant that is believed to produce fewer harmful byproducts than chlorine and also has other benefits. It maintains its disinfecting power longer in water distribution systems than chlorine, and studies have shown it to be effective at killing viruses, including SARS-COV-2. The city of Hamilton, Ohio credits chlorine dioxide with helping them win international competitions for the “best tasting tap water.”
Some municipalities have already transitioned to chlorine dioxide as a water disinfectant and others are considering the disinfectant as they plan new treatment facilities or modernizations. Additionally, chlorine dioxide is effective at removing biofilm and can be used in on-site treatment for biofilm mitigation, increasing the number of plumbing systems that could be exposed to the disinfectant.
Impact of Disinfectants on Residential Plumbing Systems
This is a noteworthy development for the plumbing industry because disinfectants in drinking water can interact with some residential plumbing materials in ways that increase the risk of failure and reduce service life. The most infamous example is polybutylene piping. This material became popular in the 1970s and 1980s, but then had to be taken off the market due to a large number of chlorine-related failures and the massive class action lawsuit that resulted from those failures.
That’s an extreme example, but certainly not the only one. PEX and copper are both subject to degradation and corrosion from chlorine. In Technical Note 53: Guide to Chlorine Resistance of PEX Pipes and Tubing for Potable Water Applications, the PPI identified multiple conditions that can accelerate chlorine degradation in PEX pipes, some of which are within a contractor’s control and some of which are not. In addition, chloramines have been linked to the development of pinhole leaks in copper pipes.
So, when a new disinfectant begins to gain momentum in the market, industry associations like the PPI provide a valuable service by analyzing the available published research to better understand the potential impact of the disinfectant on residential plumbing systems.
Key Statements from PPI TN-67
The PPI found that multiple research teams had performed various types of laboratory testing to evaluate the effects of chlorine dioxide on copper, steel, PEX, PE-RT, and PP-R piping. According to TN-67, “an analysis of the published results indicates that chlorine dioxide has the potential to reduce the service life of most plumbing distribution materials to below normal expected lifetimes.”
The only material TN-67 cites as an exception is CPVC: “Evaluation by PPI member firms indicates that chlorine dioxide is not known to be aggressive to CPVC at elevated temperatures of 200°F (93°C) and below.”
TN-67 recommends contacting each piping system supplier for guidance related to the use of their pipe and fitting material(s) in circumstances where chlorine dioxide has been selected as the disinfection chemical. Multiple PEX manufacturers have updated their guidelines to explicitly advise against the use of their products “as part of any potable-water distribution system in buildings where chlorine dioxide is used for secondary disinfection…”
The business team behind FlowGuard Gold Plumbing Systems concurs with the PPI statement that chlorine dioxide is not aggressive to CPVC at temperatures of 200° F or below. In fact, FlowGuard Gold CPVC and Corzan CPVC are the only plumbing systems marketed today as 100% immune to chlorine degradation—including chloramines and chlorine dioxide—caused by drinking water in domestic plumbing systems.
Real-World Implications
While PPI TN-67 notes that use of chlorine dioxide as a secondary disinfectant does not reflect the majority of current water disinfection practices, piping failures have already been attributed to the disinfectant in at least one municipal water system. After switching to chlorine dioxide for secondary water treatment, the city of Hamilton, Ohio, experienced high rates of failure in its high-density polyethylene (HDPE) water mains.
“We’ve got about 21 miles of HDPE piping in our system now, and it is catastrophically failing about 60 years ahead of when it should have,” the city’s Executive Director of Infrastructure, Jim Logan, told the local Journal News. “This, back about 20 years ago, was the future of water mains, and unfortunately, the chemicals we use attack the pipe and then cause it to fail.”
Note that these failures occurred in cold water HDPE systems and the temperatures found in hot-water lines can accelerate the degradation reaction in hot-water piping that is vulnerable to chlorine-induced oxidative degradation like PEX, PE-RT, PPR, and PP-RCT.
This city’s experience reinforces both the risks to some materials from incompatible chemicals like chlorine dioxide as well as the difficulty predicting future water conditions at the time materials are selected and installed. Municipalities can and do change their treatment practices for a variety of reasons and there is no way to ensure that pipes installed today won’t at some point be exposed to water treated with chlorine dioxide.
Water Compatibility and Plumbing Material Selection
Water compatibility issues generally don’t get enough attention in plumbing material selection, so TN-67 is both timely and important. For contractors that want to prevent the possibility of premature failure due to incompatibility with the material they have selected and the disinfectants being used by the local municipality, CPVC provides a safe choice.
FlowGuard Gold Plumbing Systems are immune to degradation and corrosion from chlorine, chloramines, and chlorine dioxide in drinking water. For more information on FlowGuard Gold Plumbing Systems, visit FlowGuardGold.com.
Jonathan Simon is the North American residential plumbing manager for Lubrizol Advanced Materials Inc., the parent company for FlowGuard Gold Pipe and Fittings.