Life Predictions of Elastomers in Drinking Water Distribution Systems

Because of increasing health concerns associated with the formation of disinfection by‐products such as trihalomethanes, many water utilities have replaced chlorine disinfectants with chloramines. Subsequent to this change, several utilities reported problems with substantially higher rates of elastomer failure. To predict the long‐term performance of commonly found elastomers, accelerated aging tests were conducted at combinations of three temperatures (23, 45, and 70°C) and three concentrations (1, 30, and 60 mg/L) for natural rubber; neoprene rubber; ethylene propylene diene monomer, peroxide‐cured (EPDM[P]); styrene butadiene rubber (SBR); ethylene propylene diene monomer, sulfur‐cured (EPDM[S]); and nitrile rubber. Elastomer degradation was characterized by mass change, volume change, breaking stress, breaking strain, and hardness. Using the time‐temperature superposition principle, “short‐term” test results at accelerated temperatures were shifted over time to predict “long‐term” results, generating master degradation curves at the service temperature for different disinfectant concentrations. Relatively, EPDM(P) and EPDM(S) were found to be least susceptible to chloramine degradation followed by nitrile rubber, SBR, natural rubber, and neoprene rubber.