Why Is Pool Water Cloudy? (10 Reasons, Fixes)


Underwater picture of empty swimming pool


Getting your own pool can lead to so much fun and excitement.

Many people spend years dreaming of finally being able to afford a house with a pool.

However, taking care of a pool can be more challenging than it first appears.

One of the most challenging aspects of pool care is keeping the water healthy and clear.

If you’ve noticed a change in your pool’s water, you might find yourself concerned—and with good reason!

Here is a list of reasons your pool water might be cloudy along with some potential solutions.


Why Is Pool Water Cloudy? 10 Possible Reasons


1. A Broken Filter

Control filtration system pool


It is important to keep your filter in tip-top shape if you want your pool water to be clear and appealing.

If your water is starting to look cloudy, that is a tell-tale sign that you might want to check your water filter.



Inspect your filter to identify which part of it is broken.

Order replacement parts.

If your filter is too damaged, it might be necessary to get a new one entirely.

One of the pool filter components that fails most often is the valves.

Make sure the valves aren’t damaged.

You also want to ensure the filter is correctly installed if this is a new pool or if you just had someone install a new filter.

It is best practice to get a new filter for each season of the year.

That means that you should be using your filter for three months before putting in a new one.


2. A Dirty Filter

filtration system pool


Before you go out and replace your filter, you want to make sure it is broken and not just dirty.

It is important to clean your filter regularly.

If you haven’t cleaned your pool filter in a while, try cleaning it out and letting it run before replacing it entirely.



The first thing you are going to want to do is clean the area around your filter.

Make sure it isn’t blocked or covered by debris.

Then you will want to backwash the filter.

That means running clean water through the filter in reverse.

This will help clear out any build-up in the filter.

You can also use filter cleaner to chemically clean your filter.

You should empty the skimmer basket and get rid of any debris.

You should clean your filter at least twice a year to make sure that it is functioning properly.

That is for a full cleaning, though.

For the skimmer basket, it is good to check it once each week to make sure there isn’t debris build-up.


3. Imbalance In The Chlorine

Chlorine Pellets on the edge of an inflatable pool


If you have a chlorinated swimming pool, it is important to make sure that the chlorine levels are always balanced.

If the chlorine gets out of whack, so can your pool’s appearance.



If you don’t already have a pool test kit, it’s time to get one.

You should use your pool test kit to measure the chlorine levels in the water.

Your chlorine levels should be somewhere between one and three parts per million (ppm).

If you do a strip test and it reads less than 1 ppm, it’s a sign to add more chlorine.

Once your chlorine level is balanced, the cloudiness should go away.


4. Imbalanced pH Level

Tester with tablet and powder of chlorine or bromide for maintea


Just as important as the chlorine level is your pool’s pH level.

pH is measured on a scale of 0 to 14.

Keeping the pH level balanced isn’t only about making sure your pool looks good, it also is about making sure that the water is safe to swim in.

A pH level above 12.5 pH is considered hazardous.



You are going to want to test the pH level of your pool if you notice the water’s appearance changing.

The ideal pH level for pool water is 7.6.

You can use a ph adjuster to increase or decrease the pool water’s pH if necessary.

Your water should be between 7.2 and 7.8 pH.


5. Your Pool’s Alkalinity Is Off After Adding Chlorine

Swimming pool with hot tub


You might find that you need to raise the pool’s pH level after balancing the chlorine.

That is because chlorine can lower the pH level of the water.



If you need to raise your pool’s pH level, you can do so by adding baking soda, which is also known as sodium bicarbonate.

Because the pH level of baking soda is 8, it can raise your pool water’s pH level.

The first thing you want to do is test your pool water’s alkalinity.

Ideally, pool water should be between 80 and 120 ppm.

If you get a reading of less than 80 ppm, that is your sign that you are going to need to add baking soda.

Once you have determined that you need to raise the alkalinity of your pool water, you need to calculate just how much baking soda to add.

For every 10,000 gallons of water, you will use 1.5 pounds of baking soda to raise the alkalinity by 10 ppm.

After you calculate the amount of baking soda needed, go out and buy the appropriate amount.

If you have access to a wholesale grocery store like Costco or Sams Club, these can be great places to find the large volume of baking soda you will need to balance your pool water.

Just like with many things in life, less is more when adding baking soda to your pool.

You can always add more baking soda but you can never take it away.

Start with adding half the amount of baking soda needed.

After the baking soda has dissolved into the water, do another test of the water.

Then, if it still needs more, add a little more at a time, testing as you go.

When you are adding the baking soda to the water, you are going to want to spread it around the pool instead of just dumping it all in one spot.

This will make sure that it distributes evenly throughout the water.

Your pool should have a circulation system.

Make sure that it is on to help circulate the baking soda through the water.


6. You Need To Clarify Your Pool



Adjusting the pH levels and chlorine might not be enough to fix your pool water.

Clarifying the pool is another important step to caring for your pool



You will need clarifying tablets to clarify your pool.

Clarifying tablets help get rid of microparticles and debris.

Algaecides also can help remove algae from the water.

It is important to note the algaecides are intended to remove trace amounts of algae.

If your pool is covered in algae, algaecides alone will not fix the problem.

Follow the instructions carefully when adding your algaecides to the pool.

It is best to pick a clarifier that doesn’t contain fragrances or dyes and doesn’t require complicated mixing.

Typically, pool clarifiers work within 24 hours.

Read the instructions on the pool clarifier to know exactly how long you will have to wait before seeing effects.

Make sure to let the pool clarifier finish its job before you implement another solution.


7. You Aren’t Running The Pool Pump Enough

Pool pump equipment next to brick home.


It isn’t enough to simply install a pump on your pool.

You need to make sure that you are running your pump regularly.

Your pump helps to circulate the water to keep it clean.

Not running the pump enough can result in your pool water having a cloudy appearance.



It is important to run your pool pump for at least eight hours a day.

This includes days when you are not actively using the pool.

The best way to ensure you are running your pool pump often enough is to put it on an automatic timer.


8. Heavy Rains

Abstract rain texture background. background rain in night light


Heavy rains can cause your pool to appear cloudy for a variety of reasons.

The rain can wash debris into your water.

It can also lower your pool’s alkalinity and decrease pH levels.

When pH levels are decreased, it can lower the effectiveness of chlorine.



There are several steps you are going to want to take if you notice your pool water has become cloudy after heavy rain.

Firstly, you are going to want to adjust your water level to make sure your pool is not overflowing.

When your water level is too high, the water can pull in sediment from the surrounding area, which can make the water appear cloudy.

Once you have corrected your water level, you are going to want to test the water.

This will let you know exactly what chemical imbalances you need to correct.

The two tests you should definitely run after a rain storm are an alkalinity test and a pH test.

Make sure that the alkalinity is between 80 and 120 ppm.

If it isn’t, adjust the levels using the steps listed in reason #5 in this article.

For the pH level, you want to make sure it is between 7.2 and 7.8.

If it isn’t, follow the steps listed in reason #4 in this article.

You will also want to clear out the debris from your pool.

Use a pool brush to sweep away any surrounding debris.

Then you can use your skimmer to skim any debris from the pool’s surface.


9. Your Pool Needs To Be Shocked

Hand holding Chlorine Pellets with inflatable pool on background


Your pool needs to be “shocked” regularly.

Cloudy water can be a tale-tale sign of a pool that needs to be shocked.

Pool shock is a high-concentrate level of chlorine.



Apply pool shock to your pool once a week.

Sometimes you will need to apply shock more often, for example after rain or heavy use.


10. You Have Algae Growth

Filthy backyard swimming pool and patio


The algae growth can make your pool appear cloudy.

Algae are a “diverse group of aquatic organisms” that can grow in water.

If algae are causing the cloudiness in your pool water, you will likely notice that the pool water’s color is changing as well.

If your pool is a teal-green color and cloudy, it is likely from a small amount of algae growth.

If your pool is dark green and very cloudy, the cloudiness is likely caused by a significant amount of algae growth.

If your pool is black-green and very difficult to see through, you are dealing with severe algae growth that can be difficult to kill.



The type of solution you will need to implement will depend on the type of algae infesting your pool.


A. Green Algae

This is the most common type of algae to find in a pool, but green algae are also the easiest to kill.

It is important to take care of it as soon as you notice it, though, because it can spread quickly.

Green algae typically cloud your pool water and make the surfaces in your pool appear slimy.

It can be gotten rid of by shocking and vacuuming the pool.

Afterward, you will need to shock and filter the pool water.

The amount that you will need to shock the pool water depends on how dark the algae is.

For teal green algae, you will need to use twice the amount of shock you typically use in your pool for a routine shock.

For dark green algae, you need to use three times the amount of shock

For black-green algae, you need to use four times the amount of shock.


B. Yellow Algae

This is a rarer type of algae.

It resembles pollen or sand and typically grows in the shady corners of the pool.

Yellow algae are more often found in humid environments.

Unlike green algae, it is chlorine-resistant.

When killing yellow algae, you will want to thoroughly brush and become the mustard algae from the pool.

It is best to use specific algae brush for this.

After you have brushed and vacuumed your pool, you want to test and balance the alkalinity and pH level of the pool.

It is important to balance your pool water before applying shock because it ensures the shock is effective.

Then you want to go in for a second round of brushing the pool.

The reason for brushing the pool this time is to loosen the algae and make it free-floating, so the shock can attack it more effectively.

Finally, it’s time triple shock your pool.

This should greatly decrease the amount of yellow algae in the pool.

Don’t stop at treating the pool water though! You also want to make sure to thoroughly wash your swimsuits to get rid of any pool algae that might have gotten on them.

Disinfect any pool toys with bleach.

Following your triple shock, it is important to repeatedly brush, test, and balance your pool.

Since mustard algae are more difficult to get rid of than green algae, it is important to attack in full force.

A few days after your initial triple shock, you should shock the water again.

Using one pound of shock for every 10,000 gallons of water will make sure that your pool is completely sanitized from the algae.



Remember, if you reduce the algae but don’t get rid of it completely, it will grow back.

After you have gone through the full process of tackling the algae, you are going to want to test your pool water to insure that it is perfectly balanced and the algae are completely removed.


C. Black Algae

The third and most dangerous type of pool infection is “black algae.”

Black algae are not technically algae though the problems share many similarities.

Black algae are actually caused by bacteria called cyanobacteria that affect the pool water.

Black algae look like mold when it first appears.

Despite its name, the clumps can often appear blue-green.

One of the things that make black algae so hard to kill is that it can dig into concrete surfaces.

To identify black algae, look on the surface of your pool.

Black algae do not float freely in the water.

Instead, they attach to the pool itself.

It is most commonly found on rough surfaces, which is one reason it is more common in cement pools.

It very rarely forms in vinyl or fiberglass pools.

Another tell-tale sign is that it is not easily removed with a regular pool brush.

In fact, sometimes it is impossible to remove even with an algae brush.

Black algae can be dangerous and cause health problems if you swim in it, and the effects can be even worse if you swallow water that has been infected by black algae.


Removing Black Algae

To remove black algae, you are going to want to start by cleaning your pool filter.

If possible, it is best to replace the filter entirely.

Then you will want to test and balance the alkalinity, pH, and chlorine in the pool.

You will follow this up by brushing the pool.

It is important to use an algae brush with stainless steel bristles.

You also need to exert more force than you would for a typical pool scrubbing.

Scrub the entire pool, and then focus on each spot that is not removed by the brush.

You might need to get out a putty knife to remove the remaining algae from the surface of the pool.

As you are scrubbing the algae off, you can apply a chlorine tablet directly to it.

You will need to wear protective eye gear and chemical-resistant gloves while you do it.

Simply break the chlorine tablet in half, and apply it directly to the spot of black algae, scrubbing hard.

Follow this up with another pool-wide brushing session.

Then run your pump for 24 hours.

While you are running the pump, brush the surface of your pool three or four more times.

Finally, clean the filter and shock the pool one more time.

The last step is to test and balance your pool water and to keep an eye out for any more black algae that might be developing.

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