Cloudy water can be caused by a number of factors. Check the following items in the order they appear for sources of cloudy water.
Filters must be run enough hours a day and must be clean in order to effectively remove dirt and debris from the pool water. The filter should be run a minimum of 8 continuous hours a day for halogen pools during daylight hours. When problems exist, the filter should be run continuously. The filter media (sand, DE or cartridge) must be chemically cleaned at least twice a year for chlorinated or brominated systems.
Check the filter for damage, dirty filter media and the length of time the pump is run daily. (Even if the pump is being run 8 hours a day, it may not be adequate during extremely hot weather, with heavy bather loads, or if the pump is run for short periods, then turned off, then turned back on again.)
High pH, total alkalinity, and/or total hardness can cause minerals to fall out of solution, which clouds the water. This is actually the beginning of scale build-up, and should be addressed as soon as possible. Perform a complete water analysis and follow the ALEX recommendations for proper water balance.
Sanitising and Oxidising:
Proper sanitiser residuals and normal oxidation keep bacteria and algae from growing in the pool, and eliminate undesirable compounds that can promote their growth. If these residuals drop, even temporarily, bacteria and other organisms can take a foothold and begin growing, and can cloud the water. In chlorinated or brominated pools, shock using 1 bag of Burn Out Extreme per 50,000 litres or 150 grams of Burn Out 35 per 10,000 litres. Use these products if the water is already cloudy and you suspect a growth. For regular maintenance to prevent cloudiness, you may use either of these or Lite or Oxy-Clear Pool Shock.
An inability to maintain proper sanitiser and oxidiser levels can indicate a problem and can cloud the water. In chlorinated, salt or brominated pools, test for demand.
The beginning stages of algae growth will often simply cloud the water before turning it a colour. Apply shock products appropriate for your sanitiser and add an initial dose of algaecide. Often, algae growth indicates a lapse in regular application of a preventive algaecide.
A build-up of insoluble compounds often cannot be removed by the filter. This is usually caused by inconsistent maintenance or by not shocking after heavy bather loads. Apply shock products appropriate for your sanitiser.
Solar covers or indoor pools:
Sometimes, if a pool is indoors or is kept covered most of the time, gases that normally evaporate are reabsorbed into the pool water. This re-absorption causes a phenomenon referred to as bicarbonate scale. In this situation, the pH tends to drift down and the total alkalinity drifts up, and adjustments to either are not effective. To eliminate this problem, remove the solar cover and rebalance, or for indoor pools, ventilate well and rebalance. In the future, remove the solar cover or ventilate an indoor pool several hours daily to allow the pool to gas-off properly.
Once ALL of these things have been checked and adjusted, proceed with an application of Polysheen Plus. If the water does not clear within 48 hours of continual filtration, and all of the above have been checked by a qualified professional from the store, and everything is in order, assume that there is a growth in the lines.