Control of the turbidity and concentration of free residual chlorine is of growing importance in the purification and disinfection of pool water. In general, suspended solids are removed from pool water by cycle filtration, and disinfectant is injected into pool water intermittently, depending on the concentration of free residual chlorine. In this study, various types of program swimming, in which a given number of people swain at a scheduled time, was performed in a heated indoor pool equipped with a sand filter and disinfection system using sodium hypochlorite. The variations over time of the turbidity, the concentration of free residual chlorine in pool water, and the dosage of disinfectant were measured. The variation of the turbidity over time was well evaluated using the quantity of turbid material secreted outwardly per man-hour, on the basis of the modified Muroya equation, in which the removal characteristics Of turbid material by the filter were taken into account. The calculated results accorded well with the measured turbidity. Moreover, the chlorine consumption needed to maintain a consistent level of free residual Chlorine in pool water was calculated on the assumption that the consumption consists of two parts: a part caused by swimmers and a part that was proportional to the concentration of free residual chlorine in pool water. As a result, the variation of the consumption of free residual chlorine was well evaluated. These results serve as a basis for the design and operation of a swimming pool.