In the June 23 Mailbag [“Pipe experiment misrepresents real-world plumbing scenario,” Page 6], the letter and analysis by the Plastic Pipe and Fittings Association's Dick Church contained several errors.
First, while it is true that many utilities dose water with chloramine and chlorine disinfectant at the treatment plant, the residual disinfectant may decay completely by the time the water reaches home plumbing systems.
This is one reason that the National Research Council recently identified problems in premise plumbing as a high priority for future research.
Hence, our [Virginia Tech] testing without any disinfectant is perfectly representative of what occurs in many homes. The test condition with ammonia also is representative of conditions at water utilities using chloramine or that have ammonia in their water supply.
Secondly, this research was funded by the Environmental Protection Agency and the American Water Works Association Research Foundation, in part, because of widely recognized “real-world” problems.
For example, there already has been documented high lead levels in the potable water of some homes plumbed with PVC. Nitrification is a possible contributor to this problem and the current work can provide an explanation for the elevated lead that these consumers may be exposed to.
Third, Mr. Church implies that if we continued the exposure of copper pipe “just past” 200 days, our conclusions would have been different. This is simply incorrect.
All the pipes had been conditioned by exposure to a synthesized potable water for a year before starting the 200-day experi- ment, so the effective duration of our tests was over 1½ years. We have now run these experiments in copper pipe for a total of 3½ years (over 1250 days), and there is still no evidence of nitrifying bacteria growth.
While we agree that biofilms form on the surface of all pipe systems, including copper, it has also been established that certain types of bacteria can grow on one type of pipe vs. another. That appears to be the case in the water studied for this work.
Fourth, we have conducted many case studies of homes with corrosion problems and actually documented cases in which pH dropped more than was reported.
Specifically, we recorded a drop in pH in some homes in Maui, Hawaii, from 7.89 to 6.77. In Washington, the pH dropped from 7.9 to 6.7 in some instances. We have even seen cases where the pH in home plumbing dropped to 5.2, although we do not yet fully understand the circumstances which contribute to these very large pH decreases.
The large pH drops in home plumbing have also been documented in situations where up to 4 milligrams per liter of free chloramine disinfectant residual (the highest level allowed by law) was present in the water supplied to the building.
Chlorinated PVC, plastic, copper and other water system pipes all have unique strengths and weaknesses. CPVC, plastic and copper and other pipes are all fine plumbing materials. We do not “blame” plastic or CPVC pipe for anything, but merely point out certain facts discovered in our laboratory that are consistent with several real-world problems.
We do not assert nor do we imply that these facts mean that plastic or CPVC pipe is somehow inferior to copper pipe.
It is true that the Copper Development Association is one of 20 entities that funded and/or contributed to this large research project (along with 15 water utilities, AWWA, USEPA, Montana State University and Manhattan College), but the CDA contributed only 12 percent of the project funding and was not allowed an oversight role in the research.
By participating in this project, the CDA is therefore part of a large group that is proactively responding to real-world problems that consumers may face, and is therefore going to be part of creating solutions.
Instead of providing unfounded criticism of our success in improving fundamental scientific understanding, Mr. Church and the Plastic Pipe and Fittings Association should consider taking on a similar role in future research endeavors.
Virginia Tech University