Cloudy water in swimming pools is usually caused by a chemical problem in the pool. A pool test kit is used to test the chemical balance of the water.
A low chlorine level is one of the most common reasons that a pool is cloudy. If the chlorine level is too low in a pool, the pool is not sanitized, which causes build-up in the water. Once it is determined what chemicals need to be added to the pool through use of the pool test kit, add the proper chemicals and wait four hours. The mechanical parts of the pool should also be checked to make sure the filter is clean and the pump is working.