Last Updated on March 26, 2020

A swimming pool is only enjoyable when it is clean and clear. Diving into a murky and cloudy pool is not what you want on a hot summer day. It can also be dangerous if you are unable to see the bottom or if the cloudiness is the result of bacteria. There are a number of reasons your swimming pool water can become cloudy, but there are also easy ways for you to clear it up. Imbalanced chemicals are the most common reason for cloudy pool water.

Cloudy Pool Water and What to do About It?

Imbalanced chemicals can mean 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 whereas a low pH makes chlorine very reactive which depletes levels allowing bacteria to grow. Calcium hardness refers to the excessive amount of calcium in the water and this causes scaling as the mineral 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. pH levels and calcium hardness affect the water appearance indirectly. The more direct causes of cloudy pool water include.

  • Low Free Chlorine (FC): The most common cause of cloudy pool is a low FC level. Free chlorine is that which is available to sanitize your pool water as opposed to combined chlorine which has already been used up or is diluted with ammonia. A low FC reading means you have combined chlorine in the water and this causes a cloudy appearance as well as a distinct and unpleasant odor. If the FC reading is below 3ppm then you need to shock your pool right away to restore proper chlorine levels.
  • Ammonia: When free chlorine levels drop to zero or when you have very high combined chlorine (CC)levels you could have an ammonia problem. Excess ammonia in the water will cause a cloudy appearance. When FC levels do not rise even after adding chlorine to the water, you can be assured that the water has ammonia present. To correct this, you will need to add a lot of chlorine to the pool to clear the ammonia out.
  • Algae: The buildup of algae is another common cause for cloudy pool water. You can perform an Overnight Chlorine Test to determine if you have algae or not. 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 an algae problem which causes cloudy water as it is developing.  Most pool shops carry easy-to-test kits that allow you to test all chemical levels. You can test for all chemical levels, pH and calcium hardness at once to quickly identify the cause of your cloudy water.

Cleaning the Pool Filtration System

Chemical imbalances are not always the problem as cloudy water can be caused by a dirty filtration system. 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:

  • Regularly remove particles that are clogging the filter!
  • Regularly clean and replace the filter cartridge (approximately every 1 to 2 years)!
  • Ensure all return fittings are turned down so water at the bottom can properly circulate!
  • Make sure your pump is the right size for the amount of water!
  • Most pool systems need to run 24/7 to be effective but this can vary depending on pool size.


It is also important to regularly vacuum or scrub the pool surfaces to remove accumulated dirt, algae or bacteria. Dirt, sunscreen, and body oils are potential contaminants that can cloud water if they are not removed. Use nets to remove particles that are visible and a pool clarifier for those that are not.  Nobody wants to dive into a cloudy pool. It looks uninviting and can also be a health hazard. It is best to keep your pool clean by maintaining chemical levels and following routine cleaning practices. Make sure you have everything you need to keep your pool clean and maintained so the water stays clear and you can your loved ones can swim all year through.