Water Chemistry Impact on Autogenous Metallic Pipe Leak Repair in Simulated Potable Water Systems

The impact of water chemistry (ionic strength, alkalinity, silica, magnesium, natural organic matter, dissolved oxygen (DO), disinfectants, corrosion inhibitors, and corrosion indices) on autogenous repair of 400 μm carbon steel (6.35 mm outside diameter [OD] × 890 μm wall) and 200-μm copper (6.35 mm OD × 890 μm wall) leaks were examined in modifications of a potable water at pH 8.5. Higher DO and Ryznar Stability Index significantly decreased the time to repair carbon steel 400 μm leaks by at least 50% to 70%, and chlorine dioxide produced a 300% increase in the fraction of repaired copper 200 μm leaks. Weight loss of metal pipes and presence of particulate metal rust in the water were not correlated with the time to repair 400 μm carbon steel leaks or the fraction of repaired 200 μm copper leaks. A significant fraction (15% to 38%) of the leaks repaired at 20 psi could withstand at least 100-psi water pressure, confirming the potential for an autogenous repair approach to extend the lifetime of existing water infrastructure in at least some circumstances.