2.1.1.1 Homogeneously Distributed I

2.1.1.1 Homogeneously Distributed ImpuritiesChemical impurities, small particulates, and other soluble impurities are typically expected to be homogeneously distributed throughout a distribution system because of the solubility and nature of these impurities, and because of chemical equilibrium processes. Since the impurity levels at any one location in a distribution system should be identical to the impurity levels at every other location within the distribution system, sampling for homogeneously distributed impurities may not be required at every POU and may be performed at a limited number of locations, provided that there is no likelihood of downstream sources of contamination.Homogeneously distributed impurities are candidates for continuous monitoring using on-line, in-line, or at-line instruments if the impurity levels at the instrumentation locations have been validated through sampling and laboratory analysis to be predictive of the levels at all POUs. When validated in this manner, the resulting data may be used for quality control or water release purposes. Sampling and testing of these impurities is typically done at the return of a distribution loop, but may be done in other locations. Impurities falling into the homogeneously distributed impurity category include: