Water consumption, q, in 2 apartment buildings in Koszalin (60 and 118 inhabitants, resp.) was studied. The q values and their irregularity coefficients were detd. in 2006 and 2007 at varying weather conditions, seasons and days of week as well as at changing methods for hot water supply. Replacing the individual hot water prodn. by a central supply in summer 2007 resulted in an increase in the water cost and a decrease in q. The highest q was obsd. in summer on Saturdays esp. when the rainfall was high.