Healthy water is water that does not contain substances that adversely affect the human body. Swimming pools serve as a public good, and quality of the water must meet a high standard in order to prevent any potential danger that would harm human health. It is necessary to properly and continuously carry out the regeneration of the filter mass and check the correctness of the chemical preparation system. In this way, the danger of the appearance of trihalomethanes is avoided. Trihalomethanes are halogenated hydrocarbons and are in the group of organic compounds thar are easily volatile. They are generated as a by-product of reaction of the disinfectant with an organic or inorganic substance due to disinfection. Trihalomethanes pose a danger to human health, given that compounds that exceed the permitted legal values are carcinogenic. A technique called chromatography is used to determine the presence of trihalomethanes. It separates, identifies and quantitatively determines the chemical components in water. The methods used to determine trihalomethanes is gas chromatography. They are determined by gas chromatography using MS and ECD detectors. This paper aims to determine trihalomethanes in swimming pool waters.