Nowdays human population is growing faster, and due to that there is also a growing need for basic foods without which life would not be possible. The most important factor is healthy and is water suitable for drinking. The consequence of a large increase in the number of inhabitants on Earth is the emergence of large quantities of waste water. The release of polluted and unclean wastewater into natural systems is a direct threat to the environment, but also to human health. Due to environmental protection and humans, there are legal provisions for the monitoring of waste water quality at discharge and concentrations of certain pollutants. Certain analytical methods are used to determine the concentration of pollutants in water, whose validity and precision are checked by validation methods. Validation of analytical methods provides accurate results and proves that the method serves the purpose for which it is intended. This paper presents the validation of the pH determination method, which is one of the basic parameters in the determination of wastewater quality.