1、 STATEMENT A Relative Oxidative Aggressiveness of Chloramines and Free Chlorine Disinfectants used in Treated Potable Water on Crosslinked Polyethylene (PEX) Pipe Originally adopted January 2007 Revised July 9, 2013 In a research project conducted throughout 2005 and 2006 at the request of the Build
2、ing and Construction Division (BCD) of the Plastics Pipe Institute (PPI), Jana Laboratories, an accredited laboratory, examined the relative oxidative aggressiveness of two of the most common potable water disinfectants (free chlorine and chloramines) on crosslinked polyethylene (PEX) pipes. For thi
3、s research, samples of a commercially available PEX pipe were tested in general accordance with ASTM Standard Test Method F2023 “Standard Test Method for Evaluating the Oxidative Resistance of Crosslinked Polyethylene (PEX) Tubing and Systems to Hot Chlorinated Water”. PEX pipe samples were tested t
4、o failure in a continuous-flow test setup designed to accelerate failure by using elevated temperatures and the highest levels of disinfectants allowed by the EPA. This projects test procedure deviated from typical ASTM F20231testing by using i) a test fluid containing chloramines, and ii) a test fl
5、uid containing free chlorine. Both fluids had the same 4.0 parts per million (ppm) concentration throughout the test. 1ASTM F2023 is a test method for free chlorine, with water aggressiveness controlled by the minimum oxidative reduction potential or ORP. The EPA maximum limit for each of these disi
6、nfectants is 4.0 ppm for treated potable water. For this research project, the test fluids were controlled to a pH of 6.8. Testing was conducted at elevated temperatures of 105C (221F) and 115C (239F) at 60 psig constant pressure. Testing at four (4) conditions was initiated, for a total of twenty (
7、20) specimens of the same pipe sample. Results After the testing was completed, failure times of the PEX pipe specimens tested with the free chlorine test fluid were compared to failure times of the PEX pipe specimens tested with the chloramines test fluid. The results showed pipe failure times appr
8、oximately 40% longer when tested with chloramines, compared to testing with free chlorine in otherwise identical test conditions. Conclusion Based on these results, it is the position of PPI BCD that chloramines are less aggressive than free chlorine to PEX pipes. Testing of oxidative resistance usi
9、ng free chlorine, in accordance with ASTM F2023, will provide a conservative estimate of the time-to-failure for PEX pipes when used with the disinfectant chloramines. Jana Test Report, Project 04-2256 Rev. 1 is available from the PPI BCD upon request. 105 Decker Court, Suite 825, Irving, TX 75062 Phone: 469-499-1044 Fax: 469-499-1063 www.plasticpipe.org
