Exterior Pools & Water Features

Solved! What to Do About Cloudy Pool Water

If the water in your swimming pool isn't as clear as it should be, one of three main causes is usually to blame. Your first troubleshooting step? Get a test kit.
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cloudy pool water


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Q: Every year we struggle to keep our pool water clear. The water becomes cloudy every few days, even when we run the filter 24/7. Other than this issue, the pool functions without a problem. What causes cloudy pool water, and is there anything I can do to clear it up?

A: Cloudy pool water is a common occurrence that many pool owners struggle with at least once every swimming season. The good news is that most of the fixes for murky pool water are relatively simple, but it may take some trial and error to figure what your pool’s particular problem is.

Is it safe to swim in a cloudy pool? Most of the time, yes. Cloudy water could be an indication that your pool chemicals are not balanced, and this can cause swimmers to experience red eyes, irritated skin, and rashes. If environmental factors are causing the cloudy water, it can usually be cleared up with a clarifier and regular cleaning. If, however, environmental factors have been ruled out and the water chemistry is balanced, then the problem likely lies with the filtration system. If that is the case, you may have to replace worn-out or broken components of the system. Read on to learn the common causes of this issue, and how to get rid of cloudy pool water.

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A hand holding a water test kit with pool water background.
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Learn to recognize common causes of cloudy pool water.

There are three main causes for cloudy pool water: poor filtration, chemical imbalances, or environmental factors like nearby construction, trees, or wildlife.

  • Filter and pump problems can be caused by a range of issues. If the system is run for just a few hours each day, it may not be able to clean the entire pool. If it is run regularly but the water is still cloudy, then the issue may be a worn or broken part. Other mechanical problems that can arise include clogged filter media, poor water flow directionality, or a full skimmer basket.
  • Chemical imbalances are a common cause of cloudy pool water. Testing the cloudy water with a pool water test kit can reveal whether the pool water has improper levels of chlorine, imbalanced pH and alkalinity, or very high calcium hardness levels. If your pool is cloudy after shocking, don’t be worried. A balanced pool can temporarily cloud immediately after being shocked. This typically clears quickly on its own and shouldn’t be considered a problem.
  • Environmental factors encompass pretty much everything around the pool, such as severe weather, wildlife, construction, trees, pool algae, and people. These factors can cause dust, pollen, and algae blooms to cloud the pool. If your pool is green and cloudy, the culprit may be algae. That said, people may be the most common environmental factor affecting the quality of your pool water. Not only do their various hair products, skin products, and makeup seep into the water, but people also bring dirt, sweat, skin, hair, and oils into your pool.

First, test the water.

Regular testing is essential for keeping your pool clean, clear, and safe to use, so it’s crucial to invest in an accurate pool test kit. During the swimming season, you should test your pool water for chlorine and pH at least twice a week and test for other chemicals once a week. The two most common types of tests are liquid test kits and test strips. Whichever you use, be sure to follow the manufacturer’s instructions carefully.

It’s important to know what you’re measuring, particularly where chlorine levels are concerned. In treated pool water, chlorine is present in two forms: free chlorine and combined chlorine. Free chlorine is available to sanitize contaminants, while combined chlorine has already reacted with contaminants—in a sense, it’s “used up.” Some tests measure only total chlorine (free plus combined chlorine), while others measure total and free chlorine independently. This isn’t usually a problem: In a clear pool, the amount of free chlorine will typically be about the same as total chlorine. If, however, a pool is cloudy or developing algae, even if the total chlorine measurement is fine, there may not be enough free chlorine in the water. Pay attention to what your test kit measures, and remember that free chlorine should always be higher than combined chlorine (total chlorine minus free chlorine).

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cloudy pool water

Address chemical imbalances in the water.

If testing reveals an imbalance in the chemical composition of your pool water, you need to restore the balance. This usually involves either adding chemicals or diluting the pool water by partially draining the pool and refilling with fresh water.

Test kits measure chlorine levels, bromine levels, pH levels, total alkalinity, calcium hardness, and cyanuric acid. The chemicals that affect each of these measurements need to be present in the pool water at certain concentrations to keep the water clear and safe for swimming. For instance, when levels of chlorine or bromine are too low, the concentration of these chemicals may not be sufficient to kill algae spores and could result in algae blooms and cloudy pool water. In balanced pool water, free chlorine levels should range between 1 and 3 parts per million (ppm); bromine has a slightly wider range, between 2 and 6 ppm. If the levels are too low, shock the pool with a high level of chlorine or bromine to rapidly return the pool water to a balanced level.

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Imbalanced alkalinity and pH can also result in cloudy water, and high alkalinity in particular can lead to bacteria growth and other safety issues. The total alkalinity of the pool should remain between 80 and 120 ppm, and the pH needs to be monitored.

  • A pH between 7.2 and 7.8 is best.
  • A pH between 7 and 7.8 is safe.
  • A pH of 7 or lower is considered acidic and can cause itching, burning, and rashes.
  • A pH balance above 7.8 is a basic solution that can burn and irritate the eyes.

You can raise the pH and alkalinity by adding alkaline products like sodium bicarbonate (baking soda), or lower it with chemical additives like muriatic acid or sodium bisulfate.

The calcium hardness should fall between 180 and 220 ppm. To increase calcium hardness, add calcium chloride to the pool water. To lower hardness, add a pool flocculant (such as HGH’s Drop Out Flocculant) to clump the calcium. Because these clumps will clog the filter, they need to be vacuumed up rather than left to be pulled through the filter.

Cyanuric acid is a stabilizer that prevents chlorine from breaking down under direct sunlight, which depletes the free chlorine and produces harmful chloramines. Levels of cyanuric acid should be kept between 30 and 50 ppm. Levels can be lowered by draining a portion of the pool and refilling it with clean water. Raise the levels by adding a stabilizer with cyanuric acid, or chlorine tablets that come with a stabilizer in the formula.

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If the cause of cloudy pool water isn’t chemical, examine the pool’s mechanical parts.  

cloudy pool water

When a pool clarifier doesn’t work and testing indicates that the water chemistry is balanced, then the cause of cloudy pool water is most likely mechanical. The range of possible pump and filtration problems starts with simple human error and extends to worn-out or broken parts.

During the swimming season, the filtration system needs to run for at least 8 hours every day to properly clean and filter the pool water. If it’s on for just a few hours daily, then the system won’t have time to clean the pool, which leaves the water cloudy. It’s also important that the jets point downward in order to move the water at the bottom of the pool through the system.

Regularly empty the skimmer basket and backwash the pump and filtration system to help prevent clogs. A clog in the skimmer line can reduce the flow of water through the filtration system and burn out the pump, so it’s important to turn off the system immediately when a clog occurs. To avoid further repairs, clear the clog or hire a pool repair professional to clear it before restarting the filtration system.

If human error, regular maintenance, and clogs aren’t the problem, check the pump and filtration system for any broken parts that could impact the water pressure or the ability of the system to clean debris. If any parts are severely worn or broken, they will need to be replaced. Also, the filter media can become dirty and clogged over time, so it’s a good idea to remove it periodically and clean it with an appropriate filter-cleaning product. If you find that you need to run the filter longer to keep the pool clean, or that you need to use more chemicals to keep the water clear, it may be time to replace the filter media.

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Residential inground swimming pool in backyard with waterfall and hot tub
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Explore environmental factors that could be clouding your swimming pool.

If the chemical composition of the water is balanced and the filtration system seems to be functioning normally, then the cloudy pool water may be caused by an environmental factor.

Construction and severe storms can dump high levels of dirt, dust, and other debris into the water, and large groups of people can leave behind body oils, hair, and lotions. Trees, wildlife, and algae spores can cloud the water with pollen, algae blooms, feathers, and other organic matter, making it difficult for the filter to clean the water quickly.

Fortunately, fixing environmental issues is typically as easy as adding a pool clarifier, such as GLB’s Super Blue pool clarifier, to the water. This chemical acts as a coagulant, bonding together the loose dirt, pollen, and other small particles, which increases the size of the floating debris and makes it easier for the filtration system to capture it. After applying the pool clarifying coagulant, it can take up to 24 hours for the pool water to clear up.

Despite your best efforts, some environmental factors, such as nearby construction or resident wildlife, may be outside of your ability to control. If your pool is frequently contaminated, make clarifying your pool part of your regular pool maintenance to help protect the quality of the water.

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Keep up with regular pool maintenance and chemical monitoring to prevent cloudy pool water in the future.

After your pool water issues are solved and the water is clear again, take steps to keep it that way. First, check the jets in the pool to make sure that they are angled downward so the water on the bottom of the pool circulates through the filtration system. It’s also advised to run the pump and filter for at least 8 hours every day during swimming season, and backwash the pool filter once each week.

To deal with ongoing environmental factors, use a clarifier regularly, and test the pool water two to three times per week to ensure that the chemical composition is balanced. If the tests begin to trend toward an imbalance, add the appropriate chemicals to the pool to return the pool water to a balanced state. Optimal pH for pool water is between 7.2 and 7.8, and optimal chlorine concentration is between 1 to 3 ppm.

By devoting just a little time to regular testing and maintenance, you’ll be able to keep repairs and other headaches to a minimum while you maximize your time relaxing around the pool, cooling off in the water, and living the good life. Isn’t that why you invested in a pool in the first place?