The activity concentrations of the Ra isotopes, 226Ra and 228Ra, as well as of 222Rn were measured in Austrian tap waters. Rn was extracted into a mineral oil cocktail not miscible with water and measured
by liquid scintillation counting using pulse-shape analysis for α/β-separation. Ra isotopes were co-precipitated with BaSO4 or concentrated by filtration through an element specific filter. EDTA solution was used to redissolve the precipitate as
well as to release the Ra from the filter. After mixing with a cocktail, the EDTA solution was measured by liquid scintillation
counting, too. From our results the effective ingestion doses for adults and 3 months old babies were calculated.