Calculation of reliability of water supply facilities cannot be performed if data on the reliability of separate elements are missing. One of the ways to obtain data on the reliability of elements is an analysis of statistical data on failures. In order to establish quantitative indicators of reliability of water supply networks, we analyzed statistical data on damage to water pipes in the city of Kremenchuk, Poltava region (Ukraine). The time coverage of data analyzed on the failures of the cast-iron and steel pipes with diameter of 50...300 mm was 7 years. We found the main causes of failures: for the cast-iron pipes – cement outlet from bell joints (68 %); for the steel pipes – transverse fistulas (71 %). The mean value of specific failure rate parameter and its interval estimates are calculated. The weighted average value of specific failure rate parameter, regardless of the diameter is: 1/year·km (cast iron pipes) and 1/year·km (steel pipes). Based on analysis of the received results, we built dependence graphs of specific failure rate parameter on the diameter of a pipeline. They demonstrated that with an increase in the diameter, specific failure rate parameter decreases. The obtained dependences allow us to calculate reliability indicators for other assortments of diameters of pipes. The data recieved might be useful for calculating the failure free operation of water supply systems, which determine reliability of water supply to consumers.