How to Clear Cloudy Pool Water

You’ve slipped into your cozzie and raced down to the pool, eager to dive into its cool depths. But as you’re poised at the edge, you notice something unusual. The water’s hazy, even a little opaque. At first you think it’s a smudge on your swimming goggles or the sunlight playing tricks on your eyes. Then you realise you’ve got a problem every pool owner dreads – cloudy pool water.

But don’t hang up your towel just yet! There are steps you can take to solve this problem, and it doesn’t involve draining your pool. In this guide, we reveal three common causes of cloudy pool water, what you can do to fix it and how to prevent it from happening again. Ready to turn your pool water from cloudy to clear? Then let’s dive in!

Why is your pool water cloudy?

It’s not uncommon to get cloudy pool water at least once every swimming season. The problem can come on gradually after a pool party or quickly after a heavy downpour. And while cloudiness can vary from dull and hazy to milky and opaque, one thing is certain – something is off with your pool. So what’s going on?

In short, you’ve got too many particles in your pool. This can result from dust, pollen, soil, sunscreen or algae spores. What’s more, these particles carry a negative electrical charge, which means they remain suspended in your water instead of sinking to the bottom. As a result, they reflect light and give your pool that cloudy look. There are three main reasons why this may happen:

1. Filtration issues

Your pool filter is responsible for keeping particles like dust, insects and bacteria out of the pool. When your filter is old, clogged or defective, it struggles to filter those particles, leaving you with cloudy water. This can also happen when you don’t run your filtration system for long enough. On average, your pump should run for at least 8 hours a day. Any less and your filter can’t do its job properly.

2. Chemical imbalance

If you don’t have enough free chlorine in your pool, it reduces your pool’s ability to control bacteria or algae, making your water murky or green. But it isn’t the only imbalance to look out for. High alkalinity, pH or calcium hardness can be detrimental to swimmers and pool equipment. If your pool water pH is higher than 7.8 or your alkalinity is over 200 ppm, the free chlorine in your pool will become ineffective and make your water cloudy. If calcium hardness levels are higher than 400 ppm, it can cause scaling and filter damage.

3. Environmental factors

If there are bathers in your pool regularly, pollutants like hair products, body oil, sunscreen, make-up and urine can upset the balance of your pool, making it look murky. This can also happen with leaves, dust, pollen and bird droppings. Rainfall has a similar effect, particularly if it's heavy or sustained. Not only does it dilute the chlorine in your pool, but it also adds nitrates and phosphates, making the water cloudier.

How to fix cloudy pool water

Fixing cloudy pool water can be tricky, particularly if you’re a newbie pool owner. But if you follow our four simple steps, you’ll be able to identify the root cause and get your pool back on track again.

Step 1. Check your filter

Take a look at your filter and see if it needs cleaning, service or replacing. If you have a cartridge filter, check the pressure gauge then take it out and give it a good hose down. For a thorough clean, soak the cartridge in a tub of clean water with some filter cleaner for at least 12 hours. After that, give it a good rinse and it should be as good as new! In general, cartridge filters should be replaced every two years, so keep this in your pool diary! Remember for an average size pool, you should run your filter for 6-8 hours per day in the summer, and 4 hours per day during winter.

For those who have a media filter - If it has been a few weeks or even months between backwashes, the sand filter could be due for a good backwash. The general rule of thumb is to backwash fortnightly or monthly. Chances are, you will notice that the water that comes out of your filter during the backwash is very brown and dirty. Let the backwash run for a minimum of 2 minutes or until the water turns clear on your sight glass. Sand media lasts for anywhere between 5 to 7 years. If you are backwashing your filter and still noticing dirty water coming out after 2 to 3 minutes, or no clarity in your water following a chemical treatment or backwashing a few times, this means it is time to change the sand or media.

Step 2. Check the pump

If your filters are in good shape, then there might be a problem with the pump. If it’s too small for your pool, it won’t be able to filter enough of the water regularly. The same applies if it’s too old. If you’ve had your pump for more than 10 years, it may struggle to circulate and filter your water properly. Consider getting it serviced or buy a new one. If you don’t know how old your pump is, look up the serial number or speak to a pool professional for advice.

On the other hand, if your pump is new, you may not be running it often enough. When your pool has more traffic than a Boxing Day sale in summer, your pump should run for at least 8–10 hours a day. Depending on the size of your pool, this should clear up the cloudiness in a couple of days.

Step 3. Balance your chemicals

You should be checking your pool chemistry every week, but if you’ve been negligent or life has gotten in the way, it could be the reason why your pool is looking murky. Here are some common imbalances and how to fix them:

Low sanitiser levels

Ideally, your chlorine level should be 2–3 ppm. If it’s too low, it can lead to bacteria or algal growth – a common cause of cloudiness. To fix this, add chlorine tablets or liquid chlorine. To protect chlorine levels in the future, consider buying stabilised chlorine or adding cyanuric acid (CYA). This slows down the breakdown of chlorine by UV rays and allows the chlorine to last longer in your pool.

If you don’t want to waste time taking water samples, try shocking the pool. This is great for raising chlorine levels quickly (also known as superchlorination). Preferably, do this at night so the sunlight can’t dissipate the chlorine as quickly.

High pH, alkalinity and calcium hardness

Follow our instructions in How to Test and Fix Your Pool Water to test the chemical levels of your pool. If the pH of your pool water is high, the efficacy (or killing power) of your pool chlorine is greatly reduced, which may cause the water to appear cloudy. From the graph shown below you can see that pH is an important factor in making sure the free chlorine is an effective disinfectant. To fix high pH, dose your pool with Dry Acid so that you reach an ideal pH level of 7.2-7.6.

Source: Pool Water Treatment Advisory Group

High calcium hardness levels also lead to cloudy pool water and calcification. It can be corrected with a hardness reducer, such as Calcium & Metal Remover, or fresh water from your garden hose. If you have a concrete/tiled pool, you should aim for 200 – 400ppm (Ideal 300); if you a vinyl or fiberglass pool, you should aim for 100-250ppm.  

A high TA (Total Alkalinity) causes pH and calcium scaling, both of which are associated with water cloudiness. To fix it you can add Dry Acid to the deepest end of the pool with the pump off for 2 hours before turning back on until you reach an ideal range of 100-200ppm.

Step 4. Remove environmental debris

You should start with removing any leaves, twigs, or other debris in your skimmer or pump basket. Emptying the baskets will allow for proper water flow and circulation.

Next you should remove visible leaves and dirt by using a skimmer, brushing the walls and vacuuming manually. To help things along, use a pool brush to stir the water and allow the particles to come to the surface.

If you’ve got tiny particles that can’t be removed by your skimmer or filter, use a pool clarifier. It’s available in liquid or tablet form and helps particles clump together so your filter can remove them effectively. It may take a couple of days for the debris to disappear completely, so make sure your pump runs for at least 24 hours for best results.

If you have very cloudy water, use pool flocculant. Both clarifiers and flocculants bind microparticles into larger particles, however the particles created by clarifiers are removed by the filtration system whereas flocculants require extra time and effort to manually vacuum particles that have dropped to the pool floor.

How long does it take for a cloudy pool to clear?

It all depends on the cause and severity of the cloudiness. In general, it can take up to three days for chemicals to balance, or less if you use a pool clarifier. Keep testing, run the pump and adjust the chemical balance until your water is crystal clear again.

Pro tip: If you have shocked your pool, it’s not unusual to get some temporary cloudiness. This should resolve when you run the filter for a few hours.

Is it safe to swim in cloudy pool water?

When you don’t know the root cause of the cloudiness, it’s best to play it safe and stay out of the pool. There are a couple of reasons for this. First, swimming in cloudy water doesn’t allow you to see the bottom, making diving and swimming unsafe. Second, there could be algal growth or bacteria (like E. Coli) that can cause stomach problems, urinary infections, red eyes and skin irritation. As a result, stay out of the pool until you’ve eliminated the problem and balanced the pool water.

How can you prevent cloudy pool water?

Prevention is better – and faster – than cure. First, make sure you buy high-quality products for your pool. Don’t skimp on pumps, filters or chemicals. Choose reputable brands that are suited to your pool size and type.

Second, use a cover when your pool is not in use. This will reduce debris and water evaporation, which can contribute to imbalances and cloudiness. If you can’t do this, consider trimming trees or shrubs that may be dropping pollen, leaves and seeds into your pool.

Lastly, keep up a weekly maintenance routine. This includes cleaning, testing the water, checking the pump and filter, skimming, vacuuming and shocking your pool. And don’t wait too long if you see chlorine, pH or calcium levels creep up or down. Fix them straight away or you might wind up with stubborn issues further down the track.

Wrap up

Nobody likes to wake up to a cloudy swimming pool. But it doesn’t have to spell the end of your pool party or swimming season. Whether it’s a clogged filter, low chlorine levels or tree pollen, you can get your pool back on track by following these four simple steps:

•         Backwash or replace your pool filter
•         Run your pump for at least eight hours a day
•         Balance your chemical levels 
•         Remove debris

If you’re in a rush or can’t identify the cause, give your pool a shock or use a clarifier to remove stubborn particles. Once the cloudiness is gone, keep it clear by sticking to a weekly pool maintenance schedule. Not only will it save you time and money, but it’ll keep your pool swim-ready all year round. For more information on keeping your pool in tip-top condition, dive into our Pool & Spa Guides.