AWWA JAW57847

According to this research, which was part of a larger study on the effects of metaphosphate on lead and copper solubility in plumbing systems, metaphosphate reverts more rapidly in household plumbing systems than in distribution systems. Therefore, if utility managers add metaphosphate inhibitors to drinking water, they should collect samples from both the distribution system and from consumers' taps to get a true picture in their specific system. Some corrosion, scale, and red water inhibitors contain metaphosphate, which slowly reverts to orthophosphate, in turn possibly affecting an inhibitor's effectiveness. This reversion occurs more rapidly in hard water than in soft water and is much more rapid in aged pipe than in a glass beaker. This research will affect corrosion control efforts, which are in turn driven by public health and regulatory issues. Many compliance programs involve sampling from a distribution system and consumers' taps. The apparent degree of metaphosphate reversion may be very different at a consumer's tap than in the distribution system. Includes 26 references, table, figures.