In the thesis failure analysis and assessment of water supply system in considered city was presented. The
IntroductionWater suppliers more and more often deal with the problem of maintaining water supply with appropriate parameters. It is caused by a number of factors which are inevitably associated with the development of civilization and its unavoidable consequences [1]. Losses, which appear as a cause of water pipe failure can be related to the producer as well as to the water consumers [2]. With regard to water companies losses resulting from the failure of water pipes include the cost of failure removal, including the cost of preparing to repair, its execution, inclusion repaired section to the operation and return the site to its original state, the losses associated with the volume of water unsold as a result of the failure, additional losses resulting from the failure, e.g. the costs of flooding removal, changes in traffic organization, the costs arising from responsibility of the water company to the water customers, e.g. penalties for lowering the standards of water supply to consumers and the costs associated with the maintenance the repair service in full availability [3]- [4]. The water consumer bears the costs associated with the lack of water supply, which in case of industry and services is understood as a reduced production or producing lower quality goods [5], [6], [7], in case of housing the costs are more difficult to estimate, related to, for example, the purchase of bottled water and the potential costs of losing health resulting from the difficulties in maintaining hygiene or related to the inability to use tap water to extinguish fires [8].To assess water supply network operation the failure rate is used [9], its criteria values were proposed in various studies, among others in [10], [11], [12]. In the work [12] the failure criteria with regard to reliability were presented and three classes were distinguished. The first class is characterized by the low failure rate and high reliability for the failure rate of less than 0.1 failure/km/year, the next is the average failure rate and reliability with the failure rate in the range from 0.1 to 0.5 failure/ km/year and the last with high failure rate and low reliability for the failure rate over 0.5 failures/km/year).In the study [11] for water pipes the following boundary criteria depending on the function performed by the water supply pipeline were proposed: