14. A level of 300 Bq m-3 of radon in tap water shall be established as reference level.
15. Levels of radon in surface water or in water that has been stored are extremely low, and dissolved radon in water is readily degassed once it is released from the tap. If there is a groundwater supply close to and directly linked to the drinking-water supply, with little or no opportunity for agitation or storage before the domestic tap is opened, it could be relevant to take account of radon in drinking-water in dwellings with high radon concentrations in indoor air from the ground.