Understanding the Risk of Chlorine Dioxide Disinfectant to Residential Plumbing Systems

Late last year, the Plastics Pipe Institute (PPI) drew attention to an important issue with the publication of Technical Note 67: chlorine dioxide and plastic pipes for hot and cold water service. In this document, PPI analyzes published research on the effects of chlorine dioxide on various pipe materials and provides information that every plumber should know.

Why chlorine dioxide is becoming increasingly important

Chlorine and chloramines are the most popular disinfectants used by U.S. communities to ensure drinking water safety. However, in recent years, questions have been raised about the disinfection byproducts (DBPs) that are created when bacteria in drinking water react with chlorine and chloramines during water disinfection. The U.S. Environmental Protection Agency (EPA), CDC, and independent researchers have published information about the potential health risks associated with these byproducts, which has prompted some communities to investigate alternative disinfectants.

Chlorine dioxide is an EPA-approved water disinfectant that produces fewer harmful byproducts than chlorine and offers other benefits. It retains its disinfecting power in water distribution systems longer 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 winning international competitions for “best tasting tap water.”

Some municipalities have already switched to chlorine dioxide as a water disinfectant, and others are considering the disinfectant when planning new treatment facilities or upgrades. In addition, chlorine dioxide effectively removes biofilm and can be used in on-site treatment to control biofilm, increasing the number of sanitation systems that could be exposed to the disinfectant.

Effects of disinfectants on sanitary systems in residential buildings

This is a notable development for the plumbing industry, as disinfectants in drinking water can react with some residential plumbing materials in ways that increase the risk of failure and reduce lifespan. The most common example is polybutylene pipe. This material became popular in the 1970s and 1980s, but was subsequently phased out due to a large number of chlorine-related failures and the massive class action lawsuit that resulted from those failures.

This is an extreme example, but certainly not the only one. Both PEX and copper are susceptible to degradation and corrosion from chlorine. In Technical Note 53: Guide to Chlorine Resistance of PEX Pipe and Tubing for Potable Water Applications, the PPI has identified several conditions that can accelerate chlorine degradation in PEX pipe. Some of these are within the control of the contractor, others are not. In addition, chloramines have been linked to the formation of pinholes in copper pipes.

So when a new disinfectant gains popularity in the market, industry associations like PPI provide a valuable service by analyzing available published research to better understand the potential impact of the disinfectant on residential sanitation systems.

Key messages from PPI TN-67

The PPI noted that several research teams had conducted various laboratory tests to investigate the effects of chlorine dioxide on copper, steel, PEX, PE-RT and PP-R pipes. According to TN-67, “an analysis of the published results shows that chlorine dioxide has the potential to shorten the life of most piping materials to below the normal expected life.”

The only material that TN-67 cites as an exception is CPVC: “Evaluation by PPI member companies has shown that chlorine dioxide has no aggressive effect on CPVC at elevated temperatures of 200°F (93°C) and below.”

TN-67 recommends contacting each piping system supplier for guidance on using their piping and joint materials in cases where chlorine dioxide has been selected as a disinfectant. Several PEX manufacturers have updated their guidelines and now specifically discourage the use of their products “as part of a potable water distribution system in buildings where chlorine dioxide is used for secondary disinfection…”

The business team behind FlowGuard Gold Plumbing Systems agrees with PPI's 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 – from drinking water in residential plumbing systems.

Real world impact

Although PPI TN-67 states that the use of chlorine dioxide as a secondary disinfectant does not reflect the majority of current water disinfection practices, at least one municipal water system has already had pipeline failures attributed to the disinfectant. After switching to chlorine dioxide for secondary water treatment, the City of Hamilton, Ohio, experienced high failure rates in their high-density polyethylene (HDPE) water mains.

“We now have about 21 miles of HDPE pipe in our system, and it is failing catastrophically about 60 years earlier than designed,” said the city's executive director of infrastructure. Jim Loganhe told the local Journal News. “That was the future of water pipes about 20 years ago, and unfortunately the chemicals we use attack the pipe and then cause it to fail.”

Note that these failures occurred in HDPE cold water systems and that temperatures experienced in hot water pipes can accelerate the decomposition reaction in hot water pipes that are susceptible to chlorine-induced oxidative decomposition, such as PEX, PE-RT, PPR, and PP-RCT.

This city's experience highlights both the risks that incompatible chemicals such as chlorine dioxide pose to some materials and the difficulty of predicting future water conditions at the time the materials are selected and installed. Municipalities can and do change their treatment practices for a variety of reasons. There is no way to ensure that pipes installed today will not come into contact with chlorine dioxide-treated water at some point.

Water compatibility and selection of sanitary materials

Water compatibility issues are generally not given enough consideration when selecting plumbing materials, making TN-67 both timely and important. For contractors who want to prevent the possibility of premature failure due to incompatibility with the material they select and the disinfectants used by the local municipality, CPVC is a safe choice.

FlowGuard Gold piping systems are resistant to degradation and corrosion caused by chlorine, chloramines and chlorine dioxide in drinking water. For more information about FlowGuard Gold piping systems, visit FlowGuardGold.com.

Jonathan Simon is the North American residential plumbing manager for Lubrizol Advanced Materials Inc., the parent company of FlowGuard Gold Pipe and Fittings.