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.