Cloudy water can be caused by many things. Common causes are water out of balance, a problem with the filtration system, such as old sand or broken/worn parts or tiny particles that are too small to be removed by the filter.
If your pH is too high or your total alkalinity is incorrect, the water can appear to be cloudy. If this is the case, balancing the pool water will help to solve this problem.
If you are finding that you are running your equipment all the time and there is no difference in the clarity of the water, then there is a good chance the cloudy water in your case is caused by old sand or old filter cartridges.
Sometimes the water in the pool can be filled with tiny particles that are too small to be filtered out. By adding a water clarifier, such as Polysheen plus, these tiny particles are brought together to form larger particles, thus enabling the filter to remove them and restore your pool waters clarity.