The consequences of climate changes are felt by society every day. A sudden increase or decrease in air temperature, increasingly frequent, extreme weather phenomena can cause enormous economic damage to countries and cities. The occurrence of random weather phenomena and their negative impact on technical infrastructure nowadays are the basic problem related to ensuring the safety of the functioning of each system. Climate changes and significant air temperature amplitudes have a direct impact on the functioning of the critical infrastructure of cities, which includes collective water supply systems (CWSS). The paper presents the impact of climate change on the failure of a water supply network. Correlation between failure rate and air temperature was determined. This was used to determine the number of failures for the near 2036–2050 and distant 2086–2100 future in terms of climate change (temperature increase). The results confirm the thesis known from the literature that the failure rate decreases as the temperature increases. For forecasted periods as a result of temperature rise due to climate change, the reduction of the number of water pipe failures is expected in the range of 1.22% to 2.35% for the 2036–2050 period and from 2.96% to 8.66% for the 2086–2100 period, depending on the development of Representative CO2 Concentration Scenarios (RCP). The decrease in the total number of failures will have an impact on the increase in the reliability and safety of water supply to consumers.

Water supply network is the most likely element which can fail in the whole water supply system. Failures of the water supply network often results in limitation or lack of water supply to the consumers. Identification and ranking of failure causes in terms of frequency, are the possibility to present proposals of action, related to the replacement or modernization of the water supply network. In addition, the water supply network failures were related to the main parameter important for the water consumers the time of suspended supplying in water.

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The aim of this paper is to analyse the functioning of the repair brigades in the process of failure removal in the water distribution subsystem using the mass service system (MSS). An example is presented using queuing model which takes into account notifications with various scheduling algorithms of failures occurring to the system. The functioning analysis of mass service system can be used in the optimization of the repair teams' actions and in the management of water supply companies.

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With regard to drinking water consumers, safety is understood as a probability to avoid threat arising from the consumption of water inconsistent with quality standards or the lack of water. Accordance with the Regulation of the Minister of Health water is safe for human health, if it is free from pathogenic microorganisms and parasites in the amount constituting a potential threat to human health, any substances in quantities hazardous to health and has no aggressive corrosive properties. Water supply reliability means providing stable conditions allowing to meet current and future demand for water in sufficient quantity and with required quality, in convenient time for water consumers and also at a price acceptable by them. In this study consumer (individual) risk rK was defined as the sum of the first kind of risk rKI, associated with possibility of interruptions in water supply and the second kind of risk rKII associated with possibility of consumption of water inconsistent with quality standards. Three-parameter matrix of risk was proposed. For presented method was made an application example based on exploitation data of collective water supply system, which may help to increase safety of water consumers.

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Many phenomena are characterized by unevenness and variability in time, so-called periodic fluctuations, of which seasonal variations are a special case. In water supply systems, the failures of water pipes are also characterized by unevenness during the year. Seasonality is especially evident when the failures are analysed at particular times of the year. The main purpose of this paper is to present the problems of failures in water supply network caused by seasonal changes, to determine seasonal indicators and to give an example of the system failure analysis for the selected city of south-eastern Poland. The analysis was based on actual operational data obtained from water supply company.