There are a few reasons why the wrong water temperature can affect water quality. The warmer your water gets, the more likely you are going to have bacteria grow. Bacteria love warmth, especially in wet environments. As the water gets hotter, bacteria begin to thrive, and your chlorine is eaten up. All of the chemicals in your pool are thrown off balance. You do not want people swimming in a pool with harmful bacteria.
Even before the bacteria have had a chance to grow, a pool that is too hot can be detrimental to the health of swimmers. If you stay too long in a pool which is very hot, you can become dehydrated. This is the same as staying in a hot tub for too long. You also run the risk of muscle cramps and overheating. If you keep your pool in a warm condition, then you can avoid all of these problems. And if the temperature is too cold or too hot, you will even risk damaging the pool.