This International Standard specifies a method for the determination of gross alpha activity in non-saline waters for alpha-emitting radionuclides which are not volatile at 350 °C. It is possible to determine supported volatile radionuclides measured to an extent determined by half-life, matrix retention (of the volatile species) and the duration of measurement (counting time). The method is applicable to raw and potable waters. The range of application depends on the amount of suspended matter in the water and on the performance characteristics (background count rate and counting efficiency) of the counter.