The drinking water in Hamilton, Ohio, has taken home top tap honors three times in the last 10 years for its tasteless, clean and pure qualities.
The city of 62,000 won first place for best in the country at the Berkeley Springs International Water Tasting competition in 2009. Judges for the largest water-tasting competition in the world also dubbed Hamilton's water the best in the world in 2010 and 2015.
City officials have attributed the accolades for their municipal water to using chlorine dioxide as a disinfectant going back to 1972.
The powerful chemical compound improves the taste, smell and color of water, and renders inactive pathogen agents like viruses, bacteria and protozoa, according to the U.S. Environmental Protection Agency.
However, chlorine dioxide has also made the high density polyethylene pipes in the water distribution system brittle just 20 years into what city officials expected to be an 80-year service life. Some 21 miles of HDPE pipe that have been cracking and "catastrophically failing" will be replaced at a cost of about $3.5 million in spring 2020.
"We started to see premature aging and failures in HDPE service lines around 2005 and started to see failure in water mains around 2007. I believe we informed the manufacture of this issue around 2007," John Bui told Plastics News in an email.
Bui thinks there was a period where the effect of chlorine dioxide on HDPE pipes wasn't known or publicized, and now some communities that installed them 20-30 years ago are facing failures.
"At least it wasn't known to us in the early 90's, otherwise we wouldn't have used HDPE pipes in our distribution system to save money," Bui said.
The first comprehensive report on the potential failure of PE pipes in disinfected potable water systems was issued in 2010, according to the Irving, Texas-based Plastics Pipe Institute Inc.
PPI partnered with Aurora, Ontario-based Jana Laboratories Inc. and several U.S. water utilities to look at the impact of potable water disinfectants of PE pipe.
One Jana finding indicated that there are some 52,000 water systems in the United States, and less than 200, or about 0.4 percent, use chlorine dioxide as a secondary disinfectant.
"The disinfectant ... used most often in North America is chlorine," the report says. "The other primary disinfectants commonly used include chloramines and, to a much lower extent ... chlorine dioxide. Chlorinated water, even at low levels, results in a significantly increased oxidative potential of the water."
Oxidation is a process in which a chemical substance changes because of the addition of oxygen.
Oxidation affects most piping materials to some extent, according to Camille Rubeiz, PPI's senior director of engineering for the municipal and industrial division. For example, oxidation causes metal piping systems to corrode and tuberculate, he said.
In Hamilton, the pipe failures appear to be "atypical" of HDPE pipe performance in water distribution applications, Rubeiz told Plastics News in an email.
"The concentration of chlorine dioxide [a maximum of 0.53 ppm] in Hamilton's water system appears to be significantly more aggressive than in other systems that use chlorine dioxide as a secondary disinfectant [typically less than 0.15 ppm]," Rubeiz said. "Thus, older HDPE materials that are installed in Hamilton's system have had a shorter life than the predicted service life of currently available HDPE piping materials."
Modern HDPE pipes have benefited from advances in resin design, industry research and testing to evaluate compound resistance to oxidative attack, Rubeiz said, adding that these advances "ensure that the service life of HDPE in the vast majority of disinfected water distribution systems will now exceed 100 years."
Although chlorine dioxide is making the HDPE pipes brittle in Hamilton, Bui said it isn't harmful to the people who drink it and it offers several benefits.
"Chlorine dioxide doesn't cause taste and odor like other disinfectants, such as gas chlorine, sodium hypochlorite, or chloramines," Bui said. "It prevents biofilm from forming in the distribution system, and most importantly it prevents the formation of trihalomethanes and haloacetic acids, which are considered carcinogenic."
Bui doesn't find fault with anyone or any group for Hamilton being in the position of needing to replace its HDPE pipes next year.
"We should have done more research before we decided to use HDPE pipes in our distribution system," Bui said. "I can't say whether the Water Production division was involved in the decision-making in using HDPE pipes. Once we realized, the problem we stopped using HDPE pipes. We are now using ductile iron pipes and copper pipes with brass fittings for service lines."