Blacksburg, Va. — A recent study conducted by the Civil and Environmental Engineering Department of Virginia Tech University found that various types of plumbing materials have an impact on water quality in terms of taste and odor .
“There's two things we looked at — the sensory impact and to see if the pipe material input any new materials into the water and what impact those materials might have,” said Andrea Dietrich, an associate professor at Virginia Tech who worked on the research.
The tests were conducted on copper and five polymer materials: chlorinated polyvinyl chloride, high-density polyethylene, PEX and epoxy lining.
A summary of the three-year study provided data broken down into four categories: increased odors (sensory annoyance), organic carbon release, chlorine consumption and chloramine consumption. The summary assigned a result from 1 to 5 for each category, with a 1 indicating the least impact on water quality and a 5 indicating the most impact. Dietrich said the importance of the study is in rethinking an aspect of the function of plumbing systems.
“Drinking water pipes are a type of food packaging. Just as the food packing industry looks at possible migrations from the packing material to food and the consumer, we can look at piping systems in the same way,” Dietrich said.
The study found wide differences in the effect the piping material has on the taste and smell of the water it carries. CPVC registered a 1 across the board, while the other materials scored better in some categories and lagged in others. Copper consumed nearly all of the residual water treatment disinfectant, for example, but released few organic compounds and tested in the middle of the pack for noticeable odors.
In the PEX category, the study looked at PEX-A and PEX-B, which refers to the method by which the product is produced. Dietrich declined to specify which brands of PEX were tested.
Jennifer Keller, spokesperson for PEX producer Viega North America, pointed out there are many manufactures of PEX. The company declined to comment on the study.
“I think the point of the study is that different materials will have a different impact on water quality. Both consumers and the plumbers need to know that,” Dietrich said.
Pipes made of polymer materials have increasingly been used in new construction, both for water mains and plumbing for food processing, industrial or residential use. Previous studies demonstrated that leaching of polymer additives, organic compounds and oxidation of the surface of the pipe can result in perceptible odors in both bottled and tap drinking water.
The Virginia Tech study used a panel of participants who rated the water from each different plumbing system for sensory impact.
Dietrich said water utility companies often get complaints from consumers regarding materials or odors that alter the taste of water. Sometimes the odor or taste is the responsibility of the distribution system, in which case the utility can take steps to eliminate the problem. Plumbing systems within the home are not the purview of water utilities, Dietrich said.
Even with CVPC scoring well in terms of impact on taste and consumption of chlorine and chloramine, Dietrich took pains to explain the study should not be seen as an endorsement of that material over any other.
“What I am in a position to say is the information is good for the manufacturers to know,” Dietrich said.
Determining the source of off-flavors might lead to a change in the manufacturing process, Dietrich said.
“It would be beneficial to do additional studies. This study somewhat scratches the surface, but there are a lot of products out there,” she said.