This document specifies a test method to determine radium-226 (226Ra) activity concentration in all types of water by emanometry. The test method specified is suitable for the determination of the soluble, suspended and total 226Ra activity concentration in all types of water with soluble 226Ra activity concentrations greater than 0,02 Bq l−1. The decay chains of 238U and 232Th are given in Annex A. Figure A.1 shows the 238U and its decay chain.