This International Standard specifies a method for the determination of gross alpha activity in nonsaline waters for alpha-emitting radionuclides which are not volatile up to 350 °C. The method is applicable to raw and potable waters. The range of application depends on the amount of total soluble salts in the water and on the performance characteristics (background count rate and counting efficiency) of the counter. It is the laboratory s responsibility to ensure the suitability of this method for the water samples tested.