This paper presents the impact of earthquakes on water supply and drainage networks. In the introductory part, an explanation is given for what the water supply and drainage system is used for, what parts it consists of, and which parts are observed in this paper. The impact and consequences of earthquakes on these observed parts of the system are also listed. The most commonly used vulnerability functions, which provide an estimate of the number of damage to the observed system, were analyzed. Some of the analyzed vulnerability functions were additionally analyzed and used to assess the damage to the water supply and drainage networks of the City of Petrinja, which suffered an earthquake of Mw 6.4 on December 29, 2020. Furthermore, the basic seismic data and physical-mechanical characteristics of the pipeline network were analyzed and it was explained how these data were adjusted to the values in the calculation in order to give the values closest to the real ones. The calculation estimated the value of the damage shown in the form of the number of damages per kilometer of the network length and gave an estimate of the total cost of rehabilitation. At the end, some recommendations were given on how to avoid significant earthquake damage to water supply and drainage networks.