The calibration of water distribution networks is a problem with no mathematical solution. Fuzzy logic is used in this research to capture knowledge from people who manually calibrate those networks. This way, process could become automatic. Fuzzy logic is used to calibrate simple pipes, pipes series and paths inside networks. Several initial configurations are needed in the calibration process. Fuzzy system defines and calculates the changes that should be making to topological variables, in order to improve calibration. This procedure is repeated until fuzzy system establishes that no more changes must be made. A satisfactory calibration is obtained. Finally, fuzzy sets configuration is refined to improve the system accuracy.