# 2001 Munich
A 24 Design of Experiments (DOE) test grid was run to examine the influence of the following variables on the chlorine resistance of PEX pipe; temperature, water quality (pH, chlorine concentration, ORP) and metal ions (inert vs. copper fittings). The four factors were each run at two levels and a centre point was included. A minimum of two replicates was run for each condition. A total of fifty failure points was generated. The significant factors were temperature, pH, Fitting Type, and Chlorine level (marginal). The significant interactions were pH and Temperature, and Fitting Type and Temperature (marginal). At both the chlorine levels of 3 and 5 ppm, a shift in pH from 6.5 to 8.5 is predicted to result in approximately a threefold increase in the estimated test lifetime at 60°C.