The aim of the paper is to study modern tritium levels in various sources of the drinking water supply in the settlements situated in the riverside zone of the Techa. Almost everywhere the water entering water-conduit wells from deep slits (100-180 m) contains averagely 2-3 times higher tritium concentrations than the water from less deep personal wells, slits and springs. Tritium levels in the drinking water supply decrease with the distance from the dam; while in wells, springs and personal wells they are constant all along the river. The observed phenomenon can be explained by the fact that the river bed of the Techa is situated at a break zone of the earth crust, where the contaminated deep water penetrates from the reservoirs of the "Mayak" enterprise situated in the upper part of the regulated river bed. Less deep water sources (personal wells, slits and springs) receive predominantly flood, atmospheric and subsoil waters and are not connected with the reservoirs.