The last thing you want to do is dive into a cloudy, murky pool. A swimming pool is only enjoyable when it is clean and clear If you cannot see the bottom of the pool clearly, then you have a problem. There are a number of reasons your swimming pool water can become cloudy. Luckily, there are also easy ways for you to clear it up so you can get back to swimming.

Causes of Cloudy Swimming Pools and How to Clear Them?

  • Low Free Chlorine: The most common cause of cloudy pool is a low free chlorine level. A low reading means you have combined chlorine in the water which causes a cloudy appearance and a stronger smell. You need to take a reading of the low chlorine level and if blow 3ppm then you need to shock your pool right away to restore proper chlorine levels and kill bacteria.
  • Ammonia: When free chlorine (FC) level drops to zero or when you have very high combined chlorine (CC)levels you could have an ammonia problem causing cloudy water. When FC levels do not rise after adding chlorine to the water, ammonia is likely the culprit and you will need to add a lot of chlorine to the pool to clear the ammonia out. Maintaining the FC level in your pool is the only way to prevent ammonia build-up.
  • Algae: The buildup of algae is another common cause for cloudy pool water, especially in the early stages of its development. You can perform an Overnight Chlorine Test to determine if you have algae or not. You add chlorine to the water in the evening and then take an FC reading in the morning. If the levels have dropped by 1ppm then you have the start of algae problem and the sooner you get rid of it the better Just as with ammonia, maintaining the FC levels will prevent algae build-up.
  • Imbalanced chemicals: These are the most common reasons for a cloudy pool. Imbalanced chemicals refer to too much or too little chlorine, the pH of the water, calcium hardness, alkalinity, or stabilizer levels. The pH affects cloudiness indirectly by interfering with how the other pool chemicals work. A high pH means calcium does not properly dissolve and scaling and cloudiness appear. A dramatically low pH makes chlorine very reactive which depletes levels allowing bacteria to grow and cloud the water. Calcium hardness can mean excessive calcium levels which cause scaling when it accumulates. The only way to lower calcium hardness is to partially drain your pool and refill making sure to keep the calcium hardness level between 200 and 400 ppm.

You can test the pH and chemical levels of your pool to identify if these are the reason for cloudy water. Most pool shops carry easy-to-test kits that allow you to test all chemical levels. The best kits are those that test for all chemical levels at once as this is more efficient and help you discover the problem quickly.

Clearing a Cloudy Pool from Low Free Chlorine

Free chlorine is that which is available to sanitize your pool water. Combined chlorine is that which has already been used up or is diluted with ammonia in the water, making it ineffective after killing bacteria. Total chlorine is the sum of both types. Heavy rainfall and hot sunny days can cause low free chlorine levels, so you should use a chlorine stabilizer like Cyanuric Acid if your pool is outdoors.

Cleaning the Pool Filtration System

Sometimes cloudy water can be caused by a clogged or dirty filtration system and not the chemicals. When water is unable to properly circulate, bacteria and debris can accumulate causing a cloudy appearance. To clean your filtration system and keep your water clear:

  • Ensure all return fittings are turned down
  • Make sure your pump is the right size for the pool
  • Make sure the system has been running long enough which is usually 24/7
  • Regularly remove particles or debris that is clogging the filter
  • Regularly clean and replace the filter cartridge (approximately every 1 to 2 years)


It is also important to remove particles from the pool by scrubbing or vacuuming. Too much debris or particles in the water or along the walls and floor can contribute to algae growth and cloudy water. Dirt is not the only particle to worry about as sunscreen and body oils also cause cloudy water. Use net to remove particles that are visible and a pool clarifier for those that are not. Vacuuming the sides and floor of the pool will also remove bacteria, dirt, and algae and this needs to be done regularly too. Adding Pool sanitizers will help control and prevent algae growth. Depending on what is causing the water to be cloudy, the pool may or may not be safe to swim in. Water that is murky likely does not look appealing and certain bacteria or algae can cause infection. It is best to keep your pool clean by maintaining chemical levels and following routine cleaning practices. This way your water stays crystal clear and your pool will not only be safe but very inviting.

Childproof Your Swimming Pool – Get A Pool Fence!