Everyone who uses your pool or spa may become ill if you do not disinfect your water properly. Even clear water may contain micro-organisms. You could develop ear infections, stomach aches or rashes, among other possibilities. Pool water, hot water and the small volume of spas create a favourable environment for the development of micro-organisms such as bacteria and viruses. Good hygiene reduces the number of microorganisms in the water to safe levels. To protect those who use your pool or spa, you should regularly check the water balance (adequate levels of disinfectant, pH, total alkalinity and calcium hardness). You must test the water every day, especially during peak periods.