1.1 This specification covers the required characteristics of waters deemed suitable for use with the standards under the jurisdiction of ASTM International.

1.2 The alphanumeric characters ascribed to water types and grades are specified in the manual, Form and Style for ASTM Standards.2 These have been assigned in order of historical precedence and should not be taken as an indication of a progression in water purity.

1.3 Four types of waters have been specified with three additional grades that can be applied to the four types. The grade specifications specifically address contaminants of microbiological origin.

1.4 All applicable ASTM International standards are expected to reference one or more of these reagent water types where reagent water is needed as a component of an analytical measurement process.

1.5 Although these water types and associated grades have been defined specifically for use with ASTM International standards, they may be appropriate for other applications. It is the responsibility of the users of this specification to ensure that the selected water types or grades are suitable for their intended use. Historically, reagent water Types I, II, III, and IV have been linked to specific processes for their production. Starting with the 2018 edition of this specification, these types of waters may be produced with alternate technologies as long as the appropriate constituent specifications are met (including bacteria and endotoxins, if applicable) and that water so produced has been shown to be appropriate for the application where the use of such water is specified.

1.6 Guidance for applications, the preparation, use and monitoring, storage, handling, distribution, testing of these specified waters, and validation of the water purification system is provided in Appendix X1 of this specification.

1.7 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.