The article deals with the development of mathematical model of electric conductivity of thermal power station TPS process waters. The ranges of possible temperatures of heat carrier (water) samples are given. The plots of empirical expressions in the range of temperatures from 0 to 120 °С and at higher temperatures are analyzed. The results obtained by these formulas for the temperature range from 0 to 100 °С are practically the same. The figures indicate changes in calculated limit motions of and ions depending on temperature. The calculated equation of reduction of specific electrical conductivity to the value at 25 °С for pure water is obtained.