Water supply system is a critical infrastructure. Main task of urban water system is to provide consumers with drinking water in adequate quantity, at the required quality and pressure corresponding to current standards.
For the purposes of this paper, operational reliability of the water supply system is defined as the ability to supply a constant flow of water for various groups of consumers, with a specific quality and specific pressure, according to consumers demands, in specific operational conditions, at any or at a specific time.
The main aim of this paper is to present a method for risk analysis using Bayesian process. The proposed method made it possible to estimate risk associated with the possibility of partial or total loss of the ability of water supply system operation. The paper proposes to consider two types of risk: the first type, associated with the possibility of interruptions in water supply and the second type, associated with the possibility of tap water contamination.