The main function of a municipal storage tank is to balance differences between supply and demand in order to provide users with a reliable water supply in the most economic way. Van Zyl et al (2008) proposed a stochastic analysis method to estimate the reliability of municipal storage tanks. In this study, the Monte Carlo method was used to investigate the impact of different user demand parameters on tank reliability (i.e. the probability that the tank will not run dry). In this phase of the work, sensitivity with regard to fire and pipe failures were not considered. It was found that the supply ratio, defined as the source capacity over the average demand, is the most important demand-related factor affecting storage tank reliability. It is shown that the reliability of tanks varies greatly through the year, and it is recommended that municipalities do everything possible to ensure that their system runs smoothly (i.e. all facilities are operational) during the seasonal peak demand period. Maintenance work on treatment, pumping and storage facilities should be performed when demands are at their minimum.