A pool's filter system does the work to keeping the water clean, but it takes chemistry to do the fine-tuning. It's important to carefully manipulate the chemical balance in pools for several reasons. One reason is that pathogens, such as bacteria, thrive in water. A pool filled with untreated water would be a perfect place for disease-carrying microorganisms to move from one person to another. Also, water with the wrong chemical balance can damage the various parts of the pool. In addition, improperly balanced water can irritate the skin and eyes. Improperly balanced water can also get very cloudy. There are several different chemicals that are recommended and required for pool maintenance. Chemical and Engineering Supplies Ltd provides NCP Chlorchem products for swimming pool management.