why is my pool cloudy

Why Is My Pool Cloudy? 7 Causes

The water in your swimming pool is supposed to be crystal clear and colorless. So, if yours looks milky or murky, there’s a serious problem that needs to be fixed immediately.

The first important question you need to ask before you start fixing this problem is: Why is my pool cloudy? This article discusses the 7 common causes of a cloudy swimming pool.

7 Causes of a Cloudy Swimming Pool


A cloudy swimming pool is a pool with water that appears milky and unsightly murky. There are many reasons why your swimming pool may appear cloudy. This appearance occurs when the tiny particles of impurities in your pool reflect back the sunlight.

The more particles there are in your pool water, the cloudier it appears. These particles are very tiny, ranging between 0.5 and 5.0 microns. So, they can’t be seen with the naked eye. The degree of cloudiness in your pool also varies. It can be dull, hazy, cloudy, or opaque, depending on the type and number of impurities in the water.

A dull swimming pool loses its sparkle and luster but these changes are hardly noticeable, while a hazy swimming pool allows you to see its floor without making out any details. A cloudy pool looks milky making it difficult for you to see its floor, especially the deepest area. With an opaque swimming pool, the water is completely pale, preventing you from seeing the bottom of the pool. Here are the seven main causes of a cloudy swimming pool.

1. Poor Filtration

When your swimming pool becomes cloudy, the first possible culprit to consider is your water filtration system. If the filters are not working properly, they won’t filter out the tiny impurities thus causing murkiness in your swimming pool. Poor filters will also lead to stagnation in your pool, causing more dirt to pile up.

Almost 90 percent of cloudy swimming pools are linked to poor filtration due to clogged filters. This can also be caused by a drying pump or failure to run the pump long enough. So, make sure your pool filters are working perfectly before you rule out poor filtration as the cause of the cloudy appearance.

2. Improper Chlorine or pH Levels

Aside from checking your swimming pool filters, you need to check the chlorine and pH levels in the pool water. If the levels of chlorine or pH in your swimming pool are improper, the free chlorine, which helps to remove impurities, becomes ineffective and its levels decrease. Low levels of free chlorine in your pool will result in the formation of chloramine, leading to a cloudy pool.

So, make sure that the combined chlorine levels remain below 0.5 ppm or simply under 0 ppm. The water pH in your swimming pool shouldn’t exceed 7.8. Any reading above this will render the free chlorine ineffective, allowing bacteria and brine shrimp to thrive. This not only causes a cloudy appearance but also lowers the quality of the water in your pool and makes it a perfect environment for algae to thrive.

3. Excess Alkalinity

Total alkalinity (TA) of your swimming pool water can easily cause cloudiness, especially when it exceeds normal levels. When alkalinity increases, it causes an imbalance in the pH levels and scaling of calcium, which is a major impurity in water. Your pool’s TA should not exceed 200 ppm.

Anything above this will make your swimming pool cloudy and render the free chlorine in the water useless, allowing bacteria and other organic impurities to thrive. Constant testing of your pool’s total alkalinity will help to avoid this problem.

4. Too High Calcium Hardness

Calcium Hardness (CH) is the sum of all calcium dissolved in the water. If the level of CH in your pool water is too high, it will make your pool look cloudy. This imbalance can also occur when there is an imbalance in TA or pH in the pool water.

The ideal CH level for your swimming pool should be between 100 and 400 ppm, depending on the temperature of the water. Anything above 400 ppm will cause persisting cloudiness in your pool and calcium scaling.

5. Excess Impurities from Swimmers

As people swim in your pool, they expel tiny particles that may accumulate over time to make the water appear cloudy. For instance, some swimmers use sunscreen, body lotion, and make-up that can be left in the water, causing murkiness. Body oil, bodily fluids, and perspiration are also major causes of impurities in swimming pools.

As these impurities accumulate in your swimming pool, they will reflect the sunlight, resulting in a cloudy appearance of your pool water. That’s why you should drain your pool and clean it regularly.

6. Environmental Impurities

Some environmental impurities like leaves, flowers, twigs, and other types of debris will lower the quality of water in your swimming pool, especially if the circulation of water in the pool isn’t effective. Even the tiniest debris like pollen, birds’ droppings, and dust will eventually cause a murky appearance in your pool if they are allowed to accumulate for some time.

7. Rainwater and Storms

If your area experiences regular rainfall and heavy storms, you might find your pool water looking cloudy after a while. Rainwater is known to cause nitrates, phosphates, and other mineral impurities that might cause a milky appearance. When too much rainwater gets into your swimming pool, it dilutes the free chlorine in it, making it ineffective.

How to Fix a Cloudy Swimming Pool


Although your swimming pool may look cloudy due to one or a combination of the above-mentioned causes, the process of fixing it is quite simple if you know what you need to know. Here are some useful tips on how to fix your cloudy swimming pool.

1. Fix the Filtration System

Before anything else, check the filtration system of your swimming pool to see if it’s working properly. You should keep your filters working by cleaning them regularly and replacing the broken ones immediately. Avoid a clogged D.E. filter by cleaning it once in a while.

Your D.E. filter should be washed back to remove the sand and any other debris that could be stuck in there. Don’t forget to clean the filter grids and cartridges. As you unclog your filter, remember to clean the skimmer and pump baskets. You also need to replace your swimming pool filter media immediately if it’s damaged because it’s responsible for catching impurities that make your pool cloudy.

Make sure your pool filter is running long enough so that all the pool water runs through it at least once a day.  So, your filtration system should run for about 8 to 12 hours a day. If your pool filter and pump are worn out, replace them immediately.

2. Balance Chlorine Levels

You should test the level of free chlorine in your pool water frequently and add shock to rebalance it. You should also add cyanuric acid to your sun-exposed pool water regularly to stabilize it. Regular testing of chlorine will help you to know if your pool water has enough free chlorine to cleanse it.

There are simple test strips and liquid test kits that you can use to test the level of chlorine in your swimming pool. The ideal chlorine level for swimming pools is between 1 and 3 parts per million (PPM). When testing chlorine in your pool, calculate total chlorine levels (free chlorine and combined chlorine) to get the actual reading.

Don’t forget to shock your swimming pool with calcium hypochlorite shock once in a while to stabilize its chlorine levels. Make this shock the main active agent in your pool (about 60 to 80 percent). You should shock your pool once a week, especially during peak seasons to prevent cloudiness.

Adding cyanuric acid to your swimming pool is necessary to prevent the UV rays from breaking down chlorine too rapidly. The CYA levels in your pool should range between 30 and 50 ppm.

3. Balance pH, Alkalinity, and Calcium Hardness Levels

You should test and balance the TA, CH, and pH levels in your pool water regularly. TA prevents fluctuations in the pH and calcium scaling. So, your test will help you know the amount of muriatic acid and pH decreaser to add to your pool to stabilize everything. If you want to raise your pH, you can use a pH increaser or soda ash.

If the CH levels in your pool are too high, the best thing to do is to dilute the pool water. Just drain your pool partially and refill it with fresh water from the tap. Diluting your pool affects its entire water chemistry, so you have to retest the water again for TA, CH, and pH.

4. Remove Debris, Bodily Waste, and Environmental Contaminants

Since you can prevent all debris, bodily waste, and environmental contaminants from getting into the swimming pool, you have to figure out ways to remove them before they turn the water cloudy. You can do this by treating and cleaning your pool water regularly. Test, clean, and balance your pool water after a heavy storm or when tiny contaminants like pollen and dust accumulate.

Additionally, you should skim, brush, and vacuum clean your swimming pool periodically to get rid of contaminants. For this to be done, you have to drain the pool or lower its water level. Make sure you follow the right steps when draining your pool.

Share this post

Share on facebook
Share on twitter
Share on linkedin
Share on pinterest
Share on print
Share on email

Related Posts