Balancing water systems of mines is an important element of activities undertaken by geological services of mines. Such balances are usually very difficult to carry out by means of direct measurements of water flowing into mine water systems. Therefore, indirect, computational methods based on mathematical and physical models of water systems are often used. Such calculations are most often performed with the help of computer software, using measured values of chemical and physical parameters of water types identified in mine workings areas. One such program is KYBL, which was developed as a dedicated program to balance any water system based on data describing the water compositions of those systems. Over the past 15 years, this software has been used to balance many water systems, mostly open pit and deep mine systems. The presented study attempts to evaluate the quality of balances performed using this software depending on the types of water systems studied.