The following article introduces determination method of rotodynamic pumps operation. The pumps have been installed in installations, basing on their work parameters, by means of dimensional analysis. Operation of rotodynamic pumps, as energetic devices, according to J. Girtler, has been treated as a new physical quantity of dimension, Joul multiplied by second [J∙s]. It expresses transformation of energy supplied to liquid, being forced through by the pump. This quantity can be determined, on the basis of algebraic diagram of dimensional analysis, constructed by S. Drobot. This diagram allowed us to control correctness of inference rules, in relation to mathematical aspect, used in numerical functions of rotodynamic pumps operation, fitted in instalations.