What is “cloudy” pool water?

The term “cloudy” is used to describe water that looks milky or has a murky, unsightly appearance. This is due to tiny particles in large numbers reflecting back the sunlight. These particles are so small ranging from 0.5 to 5.0 microns that they’re virtually impossible to see.

There are varying degrees of cloudy pool water:

Dull – your pool starts to lose its sparkle and lustre but the change is hardly noticeable.

Hazy – you can still see the bottom of the swimming pool but it’s difficult to make out any details.

Cloudy – your pool water looks milky and you struggle to see the bottom of the pool at the deepest section.

Opaque – you won’t be able to see the bottom of the pool.

What causes a cloudy pool?

There are several reasons why your pool water may be cloudy. These include:

1. Poor filtration

If your filter performance is compromised, your pool is going to be not only cloudy but also dirty as the water becomes stagnant. 90% of cloudy pools can be linked to poor filtration due to a clogged filter, a dying pump or simply due to not running it for long enough.

2. Improper chlorine or pH levels

Second to a dirty filter is improper chlorine or pH levels. When the pH levels are imbalanced, it renders the free chlorine ineffective and the levels decrease. Too little free chlorine forms chloramine and it is this combined chlorine that results in your pool’s cloudy appearance. It is recommended the combined chlorine level should always read below 0.5 ppm or just under 0 ppm.

A water pH excessing 7.8 will also cause the chlorine to be ineffective at killing bacteria and other natural organisms further affecting the water’s quality and risking the overgrowth of things like algae.

3. Total Alkalinity too high

Pool water with a high total alkalinity (TA) is often associated with cloudiness. This is because it can cause an imbalance in the pH levels and lead to calcium scaling. Typically if your TA is higher than 200 ppm, you’re at risk of a cloudy pool and just like imbalanced pH levels, your chlorine will be less effective.

4. Calcium Hardness is too high

Calcium Hardness (CH) refers to the sum of all calcium dissolved in the water. High levels of calcium in the water are unstable and will also be affected if there is an imbalance in pH or TA. The desired CH range is between 100-400 ppm and is temperate dependent. If the CH exceeds 400pm, persistent cloudiness will often occur as well as calcium scaling.

5. Excess particles from swimmers

Excess particles that gather during swimming could be the cause of your cloudy water. Sunscreens and oils are the most common particles found in swimming pools as well as make-up, perspiration, body oils and bodily fluids. These reflect back the light and result in the appearance of a cloudy pool.

6. Environmental debris

Environmental debris such as leaves, twigs and flowers can affect your pool’s water quality particularly if your pool water circulation isn’t optimal. Even the smallest debris such as pollen, dust and bird droppings will impact the appearance and can build up in your filter.

Looking for the best pool cleaner? Take a look at our pool cleaner guide here

7. Rainwater

If you’ve recently experienced a heavy storm and your pool water is cloudy, that’s likely to be the main cause. This is because rainwater can cause nitrates, phosphates and other chemicals to run-off into your pool. Heavy rainfall will also dilute your chlorine levels rendering it less effective.

How to clear your cloudy pool

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While there are many reasons why you have a cloudy pool, the fix is fairly simple and easy to do.

Firstly, a thorough clean of your pool to remove any foreign particles and algae is the best way to start cleaning up the cloudiness of your pool. Scrub and vacuum your pool including all the surfaces. If you have algae present, shocking your pool will assist in removing the remaining algae growth.

Find out what determines the level of pool maintenance required here

Mechanical causes

If it is a mechanical issue that is causing your pool water to become cloudy, then addressing this is your first point of call. Make sure you’ve invested in a proper filter that is suitable for the size and location of your pool. Clean the filter well and check all the parts of your filter and pump are working correctly.

Remember, owning a pool means conducting regular, routine maintenance including brushing and vacuuming your pool and checking that the mechanics are running optimally. Making sure you are running your filtration system for an adequate period of time will further clear up and prevent cloudy pool water. If you use your pool regularly, running it 24/7 will help keep the pool water clean all the time. For residential pools that aren’t used too often, running it at least 8-10 hours a day should suffice.

Chemical imbalances

Depending on the cause of your chemical imbalance, there are various solutions to help rectify the issues listed above.

Firstly, test your chlorine levels on a daily basis and adjust where appropriate. This is particularly important during summer when there are hot temperatures or you’re using the pool regularly.

If your pH levels are too low, you can use a pH increaser and a pH reducer (pH minus) will help reduce the levels if they are too high. High TA levels can also be lowered using a pH reducer. You may need to repeat this several times until you reach the acceptable levels.

If CH is the cause of your cloudy pool water, you can reduce the amount of calcium-based chlorine that you’re using to maintain your pool. A setting agent will also help reduce the quantity of calcium already in your pool.

Is it safe to swim in a cloudy pool?

Cloudy pools aren’t just unsightly, they can also be dangerous to swim in for several reasons:

1. Cloudy pool water is an indication the chlorine is not working effectively. This means there will be an increase in the presence of pathogenic bacteria and organisms like E.Coli and algae. Swimming in a cloudy pool can put you at risk of eye and skin irritation, gastrointestinal problems and urinary tract infections.

2. High chloramine suggests there are nasty contaminants such as urine, feces, blood, sweat, sunscreen and dirt floating around in your pool.

3. Depending on the degree of cloudiness, swimming in a cloudy pool can affect visibility. If you can’t see the bottom, there is an increased risk of drowning. It also can limit the view of those supervising and troubled swimmers are less easy to spot.

How can I prevent cloudy pool water?

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Stunningly clear pool by Outdoor Establishments

Regular maintenance is the best way to prevent cloudy pool water from occurring. This not only includes cleaning the pool frequently but also checking that you have the right about of chlorine and that your TA levels are correct. This will help make your water more stable against pH fluctuations.

Using quality products in your pool is also a vital component of preventing cloudy water. For example, discount brands often have weaker quantities of chlorine and this will mean you have to use twice as much to achieve the desired levels.

If you’re unsure of your pool’s chemical imbalances or the types of products you should be using to maintain a clear, sparkling pool than engaging the help of a professional maintenance team will be money well spent. It will not only save you time, it will also mean you and your family are able to swim in a healthy pool more often.

For more pool advice and tips, visit the pool section of our Learning Library.