Softeners and other salt form ion exchangers (systems regenerated with sodium chloride) should be analyzed when new and again after each two to three years of service. Demineralizer resins and other resins regenerated with acid and/or caustic should be analyzed when new and again every one to two years of service. Resins that are stored for more than a year before use should be reanalyzed before use to verify they have remained in good condition. Sample frequency should be increased for resins that are used in critical service, resins used in waste treatment, for systems that have known fouling potential, and for resins that are nearing the end of their useful lives.
Whenever possible, retain a small (500 mL) sample of all new resins for possible future comparison or analysis.