The holding time is specified by the authority governing the water sampling process for the site. The holding time is the maximum amount of time a sample can be held before analysis and still be considered a valid sample. If a sample exceeds the holding time, it is considered suspect, and the sample collection may have to be repeated.
Typically, water samples have a maximum holding time that ranges anywhere from six hours to six months. Some attributes, however, require immediate analysis, such as the following: