The purpose of this standard is to establish consistent site selection, sampling, laboratory analysis and data evaluation methods for obtaining field performance results for onsite wastewater treatment systems. This Standard provides site selection, field sampling, analytical, and statistical methods for evaluating the field performance of residential wastewater treatment systems capable of providing at least secondary treatment.

A number of field studies published in past years have varied significantly in methodology, quality, and performance results. Further, many state and local regulatory jurisdictions are increasingly interested in field performance data to compliment lab performance data. While NSF/ANSI 40 and 245 remain a valuable demonstration of initial product performance under defined conditions of test, the addition of field data can further demonstrate system performance when subjected to the variability of individual residences.

This Standard was developed by the NSF Joint Committee on Wastewater Technology using the consensus process described in the American National Standards Institute.