Water intake on the Karelian Isthmus and in the northern part of Saint-Petersburg is extensively based on groundwater, so the water quality is the main limited parameter. By major components (about 350 points were included into consideration) groundwater generally satisfy the requirements for centralized service, if salinity is less than 0.8 g/l. By microelements (∼ 240 points) groundwater is usually good. Exceptions are Fe and Mn whose abundance exceeds the regulative level in quaternary aquifers and somewhere in Vendian complex (which is mostly protected against anthropogenic pollution). Water partly not fit to drink takes about 25% and F, Ba, B are the limited components. Natural radioactivity (∼ 150 points) is usually less than the response level, but sometimes activity of 226Ra exceeds the response level by 30 times, so the abundance of radionuclides should be checked in each case.