Polyethylene pipes exposed to chlorine dioxide in drinking water supply system: A critical review of degradation mechanisms and accelerated aging methods

Polyethylene (PE) pipes have been widely used in drinking water distribution systems across the world. In many cases, chlorine dioxide (ClO2) is used to maintain a residual disinfectant concentration in potable water. Practical experiences have shown that the lifetime of PE pipes is significantly reduced due to exposure to drinking water with ClO2. Recently, many companies have proposed new PE pipes with a modified formulation, which are more resistant to chlorine dioxide. However, a standardized test method for evaluating the long-term performances of PE pipes is still missing. This literature review was performed to provide a description of chlorine dioxide uses and degradation mechanisms of polyethylene pipes in real water distribution systems. Current accelerated aging methods to evaluate long-term performances of PE pipes exposed to ClO2 are described and discussed along with the common technics used to characterize the specimens. Accelerate aging methods can be distinguished in immersion aging tests and pressurized pipe loop tests. Wide ranges of operational conditions (chlorine dioxide concentration, water pressure, water temperature, etc.) are applied, resulting in a great variety of results. It was concluded that pressurized looping tests applying semi-realistic operational conditions could better replicate the aging mechanisms occurring in service. Despite this, the acceleration and the evaluation of the long-term per-formance are still difficult to determine precisely. Further experimentation is needed to correlate chemical-mechanical characterization parameters of PE pipes with their lifetime in service.

Automated summary

Polyethylene (PE) pipes, widely used in drinking water distribution systems worldwide, have been found to have reduced lifetimes when exposed to drinking water with chlorine dioxide (ClO2). Though new PE pipes with improved resistance to ClO2 have been proposed, a standardized test method for evaluating their long-term performances is still missing. This literature review explores the uses of chlorine dioxide and the degradation mechanisms of polyethylene pipes, as well as various accelerated aging methods used to evaluate their performances. It is concluded that pressurized looping tests applying semi-realistic operational conditions may better replicate aging mechanisms observed in service. However, accurately determining the acceleration and evaluation of long-term performance remains challenging, requiring further experimentation to establish correlations between chemical-mechanical characterization parameters and the lifetime of PE pipes in service.