Type I pitting of copper tubes from a water distribution system

Samples of copper tubes from a cold water distribution system which had failed due to pitting whilst in service were subjected to a detailed failure investigation. Analysis of the tubes showed that failure was a result of Type I pitting attack. While the exact cause of pitting was unknown, it was hypothesised that it could have been due to changes in the water quality and/or content. The tubes were found to be made from phosphorus de-oxidised copper and no anomalies were evident in either the chemical that composition or the microstructure which could have caused the pitting observed. It was recommended that the tubes be replaced and that due attention be given that the new tubes are free of internal carbonaceous deposits or other foreign matter.