Cloudy water is a common problem that occurs in a swimming pool. There are many possible factors as to what causes it, like an inoperative filter, algae, debris, imbalanced pH levels, and other chemical problems.
As pool owners, it is our responsibility to understand common pool problems, its implication, and solutions.
In this article, we will talk about all the causes of cloudy pool water and how to solve each one.
Summary Of Causes And Solutions
| Cause Of Cloudy Water | What To Do To Clear A Cloudy Pool? |
| Inoperative Pool Filter | Check if the pool pump is runningCheck if the pump lost its primeCheck for leaks Check for clogged filter and pipeFix all the found problemsReplace defective parts |
| Low Free Chlorine Level | Test the levels of chlorine using test kitsBalance pH and cyanuric acidpH – 7.2 to 7.8Chlorine – 1 ppm to 3 ppm Cyanuric – 15 ppm to 70 ppmAdd chlorine |
| Imbalanced pH levels | Test if basic or acidicIf basic, add dry acid or muriatic acidIf acidic, add sodium bicarbonate |
| High Calcium Problem | Drain and replace with fresh waterUse water softenersGet filtering services |
| High Alkalinity | Balance pHAdd dry acid or muriatic acid |
| Algae Bloom | Balance pH, run the pump, and scrub the poolPool shockUse algaecide and do a deep clean |
| Ammonia | Pool shock until the level of chlorine is stable |
What Is Cloudy Pool Water?
As the term implies, cloudy pool water refers to a milky, murky, or unclear state of water in your swimming pool. Pool water can be called cloudy if you can’t see the bottom of the pool.
The reason for this cloudy appearance is due to solid particles dissolved in the water of your cloudy pool. These small particles that can’t be seen by the naked eyes prevent sunlight from passing through the water. Thus, creating a cloudy, milky, or unclear appearance making you unable to see the bottom of the cloudy pool.
Usually, these small solid particles diffused in the water are filtered out by the filtration system of your pool. So a cloudy pool can be due to a problem in the pool water filter.
There are also many possible causes that contribute to a murky water appearance. Some of these are low levels of chlorine, algae, debris, and imbalanced water chemicals.
We will be tackling each one of these problems in-depth further in this article.
Is It Safe to Swim in a Cloudy Pool Water?
No, it is not safe to swim in a pool filled with cloudy water. The causes of the murky water are no ideal for you to swim in. Here are some of the possible health implications.
Low Free Available Chlorine Level (FAC)
Swimming in a water-filled cloudy pool that has a low chlorine level is not good for your health. Remember that chlorine serves as your water disinfectant.
When chlorine is put into the pool water, they interact with living organisms like bacteria. Chlorine molecules destroy the organism’s cell membrane, effectively killing the organism’s cells. Thus, keeping the pool clean. Also, chlorine oxidizes metals and other minerals that are harmful to humans once ingested.
After this chemical interaction, the used up chlorine molecules won’t be able to deal with other organisms. The used-up chlorines are called combined chlorine or chloramines. Chloramines and free chlorine make up for the total chlorine count in the swimming pool.
Those chlorine molecules that are still available for destroying harmful organisms are called residual free chlorine. Maintaining the right levels of residual free chlorine is a must to keep your pool safe to use.
But you may be maintaining proper chlorine levels, but the water is still cloudy. One thing you can check is the level of cyanuric acid. Although cyanuric acid protects chlorine from sunlight, it also weakens the cleaning/sanitizing effect of chlorine. You can check our in-depth article here on our website that talks about cyanuric acid in detail.
Presence Of Algae
Swimming in a cloudy pool filled with algae is not a good idea even if the common green algae by itself are not harmful to humans. The problem with common algae is that it serves as a home for microbes that negatively affect human health.
There are also other types of algae that can be harmful to humans, like cyanobacteria. Cyanobacteria, when left untreated, produce cyanotoxins that can be harmful to humans. Effects of cyanotoxins are vomiting, conjunctivitis, rhinitis, earache, sore throat, and other gastrointestinal problems. Other harmful algae are dinoflagellates and diatoms.
Common Reasons for Cloudy Pool Water – Testing and Solutions
You will find below common reasons as to what causes cloudy pool water and the solutions that you can do to clear cloudy pool water. If the cloudy, murky, or milky pool water problem still occurs despite following the guide below, it is time to call for professional help.
Inoperative Pool Filtration System
During troubleshooting to fix cloudy pool water, the first thing to check is the pool filter. A properly working filter system is crucial when troubleshooting other causes of cloudy water.
Inspection and Testing
As you already know, a pool filter is essential in removing the debris and particles in the pool. These particles and debris contribute greatly to making the pool cloudy. Thus a faulty pool filter and a faulty pool pump will lead to the accumulation of debris and particles in the pool.
Here are some of the things to check if your pool filter system has problems:
- Abnormal pressure of the pool filter
- Leaks on the pool filter
The filter pressure gauge will indicate whether you have a good water flow in your system. Low water pressure can indicate that your pool pump is not running or there are severe leaks in the filter system. High water pressure can indicate a clog in the filter or the pipe.
Leaks on the pool filter system indicate if there are certain problems like clogging or defective valves. Water leaks in the pool filter system cause inefficiency and lets air enter into the system.
Both of these problems lead to particles and debris accumulation that can make your pool cloudy. So read on as we talk about solving these filter problems further below.
Solution
To clear cloudy pool water due to inoperative pool filters, follow the guide below.
Low Pressure of the Filter
Let us talk about a low-pressure reading first. The pressure of your pool system will depend on your setup so refer to your manual or instructions left by the installer or manufacturer. As a reference, the normal pool filter pressure is 10 psi to 25 psi.
So when you notice that water pressure is low or zero on the filter gauge, it can indicate three things: the pool pump is not running properly, a pool pump leak, or there is a clog before the pool pump.
To troubleshoot if the pool pump is working correctly, get a multi-tester. Test and verify if the power supply to the pool pump is ok. If there is no voltage reading, then the breaker is faulty, or the wiring is cut. Replace these parts as needed.
If the voltage is ok, then check if the water pump is running when the supply is on. If it does not run, conduct an insulation test and ground test using the multitester. These tests will tell if the windings are ok. If the test indicates that the windings are burnt, either get a new pool pump or get a rewinding service for your pump motor.
If the pool pump is running ok, but the water pressure is still low, the pipe before the pool pump probably lost its prime or the pipe has a clog. Prime the pool pump as needed and run it again. If the pressure is still low, the pipe has a clog. Unclog the pipe, and you’re good to go.
High Pressure of the Filter
A high-pressure reading on the pressure gauge usually indicates a filter clog, or there is a clog in the pipe or valve after the pool pump.
For a sand pool filter and diatomaceous earth filter, you can sometimes remove a clog by just backwashing. If you have a cartridge filter type then you can’t backwash it.
If the clog still persists after backwashing, the best way to resolve this is to disassemble the pool filter, valves, and pipes then check each part for a clog. Remove the clog and clean the filter before reinstalling. Run the pump and filter and check if the pressure is good and the filter is working properly.
Water Leaks in the Pool Filter
Spotting water leaks in the pool filter is easy because usually there are wet stains where the leaks are present. Prepare replacements for the parts once you find the leak. Usually, leaks are found in pipe joints, valves, clamps, and fittings. After repair and replacement, run the pump and filter to check if there are no more leaks.
Low Free Chlorine Level (FAC)
Inspection and Testing
Like what we’ve talked about earlier when the water in a pool has a low chlorine level, many bacterias, minerals, and metals remain. These particles, debris, organisms, metals, and chemicals that should’ve been killed and oxidized are now accumulating slowly in the water.
These accumulating particles blocks sunlight from entering the water. Thus, making the pool look cloudy or milky.
Again we remind you that swimming is not advisable in cloudy water. Complications that can arise from swimming in a pool without disinfection can result in skin rashes, severe vomiting, ear infections, diarrhea, and urinary tract infections.
To start the troubleshooting of cloudy water in your pool, measure the free available chlorine using test kits or by using automatic sensors or devices.
Using sample test kits are the cheapest way to test for residual free chlorine in the pool water. On Amazon, test kits usually cost around $10 to $15. The test kits usually come with chemicals or reagents that you’ll add to the sample pool water. If you want automatic pool chlorine meters for convenience, you can find one on Amazon, and they usually cost around $100 to $200.
Before getting your sample water in the pool, turn on the pool pump first to circulate the pool water. Then get the sample water from the supply inlet to the pool.
If you are using the automatic chlorine meter, you just need to turn on the device and dip the test probe of the device and it will automatically read the available free chlorine and combined chlorine of the water.
But if you are using the chlorine test kit, get the gauge canister and open the lid. Fill in the gauge canister with pool water halfway. Then, read the instructions included on the test kits on what reagents to mix with the pool water. It usually involves putting a coloring reagent then counting the other reagent drops until the color disappears from the sample water.
Solution
To clear cloudy pool water due to lack of free chlorines, there are multiple solutions depending on the test results.
The first and most simple scenario is that the test result shows that the pool has low free chlorine levels but low combined chlorine. Combined chlorine or chloramine levels should only be 0.5 ppm and below. The solution is adding chlorine to the water of the swimming pool.
But if the results show that you have low chlorine levels but have high combined chlorine levels, then you should check two things. The first one to check is your chlorine pool stabilizer level or cyanuric acid level.
The Center for Disease Control and Prevention (CDC) recommends only 15 ppm of cyanuric for commercial pools. But for a home swimming pool, you can range from 30 ppm to 70 ppm, and you’ll just be fine. A high level of cyanuric in water will greatly weaken the disinfecting abilities of chlorine.
Use a test kit that measures cyanuric levels to know the amount of concentration. If the cyanuric acid exceeds the mentioned concentration range, then one of the best ways to lower it is to drain the pool water and add fresh water. It is advisable to drain the pool water completely if the concentration of cyanuric exceeds 100 ppm.
If cyanuric levels are low, then shocking the pool will solve the cloudy pool problem. To shock a pool, you need to dose the pool water with a large amount of pure chlorine (without stabilizers). It is recommended to use sodium hypochlorite in doing this. Keep the pool pump running during the shocking process to filter out other debris and particles.
Imbalance of pH levels
Another reason for cloudy pool water is an imbalanced pH level. The pH or power of hydrogen refers to how basic or acidic your pool water is. The ph scale goes from zero (0) to fourteen (14), with zero being the most acidic and fourteen being the most basic.
Acidic water is corrosive and makes chlorine more reactive. Making chlorine much easier to react with sunlight and escape as a gas into the atmosphere. This will lead to low free chlorine count and the growth of unwanted organisms that can cloud the water. Acidic water also damages pool equipment.
Basic water on the other hand clouds the water by making lime and calcium precipitate. When lime and calcium precipitates it will lose its solubility and will become clumps of particles floating in the water.
To avoid cloudy water in your pool, it is important to balance the pH level. Changes in the pH of the water are due to the usage of chemicals used in the pool.
Inspection and Testing
Testing the pH of your pool water is easy. It is available in almost all of the available types of test kits. Just take sample water and apply the reagents. Wait for the color to appear and compare it with the color guide to determine the level of pH.
Solution
The goal is to achieve a pH of 7.2 to 7.8 as recommended by the CDC. Below are two scenarios as to how lower or raise the pH of your pool water and fix a cloudy water.
Lowering The Level Of pH
If your pH test turns up a high result, meaning water in the pool is basic, then you can use two options in lowering pH. Both options involve using acid so make sure to wear proper protective equipment for your safety.
The first one is by using sodium bisulfate or dry acid as its commonly called. Carefully read and follow the instruction manual as you ready the needed amount of dry acid. Before putting the acid in the pool, run the pool pump and filter, and make sure that you are applying it downwind to prevent the dry acid from blowing back into you. For quicker results, apply the dry acid near the return jets. Do not pour chemicals directly into the pool skimmer.
The second one is by using muriatic acid. The methodology is just the same, read the instructions included in the product. Prepare the correct amount and pour it next to the return jets. Do not pour chemicals directly into the pool skimmer.
Raising The Level Of pH
If your pH test turns up a low result, meaning water is acidic, then the solution is to use sodium bicarbonate or baking soda in common terms.
To use sodium bicarbonate, first, prepare the needed amount. A general rule of use is that 1 pound of baking soda will raise alkalinity by about 10 ppm in 10,000 gallons of water. To be sure, you can use online calculators to know how much is exactly needed. Mix baking soda into water and pour near the return jets. Do not pour directly into the pool skimmer because it can clog up your pool pump and filter.
High Calcium Hardness
Another probable reason as to why your pool is cloudy is high calcium hardness. Calcium hardness is the measure of how many dissolved particles of calcium and magnesium are in your swimming pool.
These calcium and magnesium particles cloud the water at high levels. Maintaining the calcium hardness at an ideal level also prevents the forming of scales in the pool and your equipment. The ideal calcium hardness for pool water is 150 ppm to 400 ppm (depending on water pH level, temperature, and alkalinity).
Calcium and magnesium particles may be coming from water supplied by your water supplier. It can also be from adding calcium hypochlorite (a type of chlorine) in your pool water.
Inspection and Testing
Before testing for calcium hardness, it is necessary to check balance first the chemical properties of your pool water – pH level and total alkalinity. The ideal pH level is around 7.2 – 7.8 while total alkalinity should be around 60 ppm to 120 ppm.
Take note the when using test kits, there is a kit that measures total hardness and calcium hardness. These are two different things. Total hardness refers to calcium and magnesium count. While calcium hardness only measures the calcium count.
For those who are using test strips, run the pool pump and filter for a while and dip the test strip into the water, and wait for the color to appear. Compare the color to the guide included in the test kit package.
For those who are using the test kit with chemical reagent drops, run the pool pump and filter for a while and collect a water sample from the return jet.
Solution
To clear a cloudy pool due to high calcium hardness, follow the steps below.
If your water supply has the right amount of calcium hardness, fixing high calcium hardness is easy. Just drain and refill with fresh water. Or if you want to be efficient, you can just drain partially to dilute the water hardness.
But if the water supply in your area is also hard, then you can opt to use water softeners. Water softener systems can be costly but it is a wise investment since you can also use water softeners in other household chores.
There is also a precipitation method to lower calcium hardness, but it can be quite hard to do since it involves raising your pH level to more than 10. So we recommend not doing it by yourself.
In some areas, there are companies that sell treated water specifically for pool. And there are also companies that offer filtering services to correct the chemical properties of pool water.
High Alkalinity
Alkalinity refers to the measure of the resistance of an object to acids. Thus, alkalinity affects the pH of the water in your pool greatly. When alkalinity is high, lime and calcium precipitate leading to cloudy water in your pool.
Inspection and Testing
To test for alkalinity in a cloudy pool, you can use pool test kits that have alkalinity tests. Get sample water from the return jets and mix them with the coloring reagent. Afterward, count the number of the reagent drops needed to remove the color. The number of drops will be multiplied to a factor that is specified in the test kit manual.
Solution
If the test results show that you have high alkalinity, there are two methods to lower alkalinity.
The first one is by using sodium bisulfate or dry acid as its commonly called. Carefully read and follow the instruction manual as you ready the needed amount of dry acid. Before putting the acid in the pool, run the pool pump and filter, and make sure that you are applying it downwind to prevent the dry acid from blowing back into you. For quicker results, apply the dry acid near the return jets. Do not pour chemicals directly into the pool skimmer.
The second one is by using muriatic acid. The methodology is just the same, read the instructions included in the product. Prepare the correct amount and pour it next to the return jets. Do not pour chemicals directly into the pool skimmer.
Ammonia Turning Into Nitrates
Ammonia is a natural-occurring alkaline gas in the atmosphere. It is highly soluble, colorless but has a distinctive bad smell. This gas is a molecular compound that has a formula of NH3 (one nitrogen atom and three hydrogen atoms).
The usual source of ammonia that enters your pool is from precipitation. Ammonia from agriculture, industrial processes, livestock manure, and agricultural fertilizer mixes with atmospheric air. These particles of ammonia come down back to Earth when it rains. Ammonia can also come from bacteria that accumulated in the water of the pool. Other sources of ammonia are debris, animals, and humans that enter the pool.
When ammonia enters the swimming pool, it reacts with the chlorine to form chloramines. Aside from chloramines, the result of this chemical reaction results forming of nitrites then further into nitrates.
Ammonia in a high amount is bad for your pool. It will make your pool cloudy because it will consume all the available free chlorine and turn it into chloramines. Resulting in the growth of algae and other harmful organisms.
Inspection and Testing
There is no direct testing for ammonia in a pool because like what we talked about earlier, ammonia does not stay for long in a pool. It quickly reacts with chlorine to form chloramines and nitrates.
So to check for ammonia in your pool, grab your test kits and test strips to check for levels of free chlorine, combined chlorine, and cyanuric. Here are the signs to check:
- Low to zero free chlorine levels
- High chloramine count or combined chlorine
- Pool water has a bad odor
- Low cyanuric (CYA) levels
Solution
Once you have confirmed that your pool has an ammonia problem, the next thing to do is prepare the materials needed for a pool shock. Prepare liquid chlorine and sodium hypochlorite, a test kit or test strips, and cyanuric acid.
Prepare a large amount of chlorine because a pool shock needs to reach a concentration of 10 ppm and above. We recommend using liquid chlorine because it doesn’t affect other water qualities like pH level, hardness, and CYA levels.
The commonly available test kit can only measure up to 5 ppm of free chlorine levels. So you should check if your test kit is able to measure more than 10 ppm.
Begin by preparing the right amount of liquid chlorine. As a rule of thumb, 1 oz of pure chlorine will raise a 10,000-gallon pool by 1ppm. Usually, liquid chlorine is in a 10% concentration so dividing 1 oz by 10%, you’ll need 100 oz of liquid sodium hypochlorite to raise a 10,000-gallon pool by 1 ppm.
Run the pump and filter and pour the right amount of chlorine to raise the chlorine concentration by 10ppm. Then measure every 20 minutes using the test kits. If free chlorine level falls below 5 ppm, then add chlorine as necessary.
Repeat until free chlorine becomes stable around 5 ppm. Once stable, apply cyanuric acid to stabilize the chlorine.
Algae Bloom
Algae are aquatic organisms that have the ability to photosynthesize. That is why an algae problem is a common problem for an outdoor pool.
Algae are very hardy and can live under extreme conditions. They can grow in bodies of water that have high acidity levels, extremely cold weather, high water pressure, and thin oxygen levels. So dealing with it can be hard, especially when not prevented early.
Algae can easily spread due to their fast reproduction. They can reproduce through asexual or sexual methods that produce a large number of spores. These spores are easily carried away by the wind and animals, so it’s very easy for your outdoor pool to have algae.
Inspection and Testing
Algae problems are caused by several factors like low free chlorine, poor water circulation, imbalanced pH level, bad filtration system, and lack of preventive maintenance.
The usual algae in the pool are the green ones, which are quite safe but should still be treated. For a swimming pool, algae are usually identified by the color – green, yellow, and black. But like what we talked about earlier, there are other types of algae that you should be aware of because they are harmful, like cyanobacteria, diatoms, and dinoflagellates.
Having an algae problem in your pool can be easy to tell. Usually, the swimming pool water will have a tinge of yellow-green, yellow, or orange.
Aside from the water’s color, another way to check if there are possible algae in your pool is by doing the overnight chlorine test. The overnight chlorine lost test is done to verify that there are organisms like algae that continuously consumes your chlorine.
To do the overnight chlorine loss test, you’ll need a FAS-DPD test kit. If you have an automatic chlorinator in your pool, turn it off and measure the free chlorine and combined chlorine using the FAS-DPD test kit. Record the results and wake up early in the morning before the sun rises and measure again.
Compare the results take at night and in the morning. If the difference between the free chlorine is less than or equal to one, then you don’t have an organism in the pool that consumes chlorine. But if the results say otherwise, you have algae or other living organisms in the pool that consume chlorine.
Solution
The first step to fix cloudy pool water caused by the algae bloom in the swimming pool is to run the pool pumps 24/7 and balance first the water properties in the water. These properties are pH level, chlorine concentration, and cyanuric levels.
Here is a list of the ideal range of water properties that you should follow:
- pH level – 7.2 to 7.8 (recommended by the CDC)
- Chlorine level – 1 ppm to 3 ppm (recommended by the CDC)
- Cyanuric level – 15 ppm to 70 ppm
After balancing and running the pump for a day, scrub the swimming pool’s stairs walls, floor, and vacuum to remove the algae. As you scrub push it towards the main drain of the pool.
Afterward, keep the pump running and shock the swimming pool with calcium hypochlorite. Calcium hypochlorite is a pure disinfectant and is an effective removing agent of algae. Usually, 30 ppm of calcium hypochlorite is needed to shock and clear a cloudy pool. To hit the 30 ppm amount, follow the instructions included with the hypochlorite.
Leave for the day and keep the pump running. Test again using the FAS-DPD test kit to know the pH level and chlorine concentration. If the free chlorine results show 0 ppm, shock the pool again and leave for the day.
If the problem persists, you can use an algaecide as a last resort and then scrub the pool hard. After the hard scrub on the swimming pool, vacuum the algae clout that will settle in the pool water, preferably straight to the wastes.
Should I Use Pool Clarifier and Pool Flocculant?
Yes, but we recommend using a pool clarifier and pool flocculant (pool floc) as a last resort method to fix cloudy water in the pool.
How to Use Pool Clarifier?
A pool clarifier acts as a binder for all the debris and particle that is too small for your pool filter. After the binding of the debris, your filter will now be able to remove it.
Using a pool clarifier is easy, start the pump and pour a healthy amount on the perimeter of the pool water. Leave it for a while, and you’ll be able to see the bottom of the pool again.
How to Use Pool Flocculant?
A pool flocculant, or pool floc, is like a pool clarifier but it sinks all the clumped debris and particles at the bottom of the pool. So if you don’t have a drain at the bottom of the pool, you have to manually vacuum out the debris and particles that settled at the bottom of the pool.
To use a pool floc, run the pump and filter, and pour a healthy amount at the around the ground pool.
Easy Preventive Maintenance Tips Against Cloudy Pool Water
To prevent cloudy water and maintain clear water in your pool, it is a must to have regular preventive maintenance.
- Conduct daily testing and balancing on water parameters like pH, chlorine, and hardness
- Conduct a weekly ground pool cleaning and visual inspection for signs of algae, leaks, and pool equipment problems
- Conduct a weekly non-chlorine shock on your ground pool
Frequently Asked Questions
Why Is the Pool Cloudy After Chlorine Shocking?
A pool can remain cloudy despite shocking due to a number of reasons. Like if the pool pump and the filter are not running. It can also be that the chlorine shock is not enough, conduct repeatedly until chlorine levels are stable.
Can Baking Soda Clear My Swimming Pool?
Using baking soda can resolve one of the causes for a cause of cloudy water, which is acidic water.
Why Is My Pool Cloudy After Rain?
Rain introduces ammonia and other unwanted contaminants to the swimming pool. Ammonia uses up free chlorine at a fast rate. And that is why you need to shock a pool when a pool remains cloudy after rain.
Can Too Much Chlorine Cause Cloudy Water?
Yes because too much chlorine can upset the balance of the water properties like pH, hardness, and alkalinity.
The key to fixing cloudy pool water and having a crystal clear pool of water is by balancing pH, chlorine levels, and a properly working filter system.
With our guide on how to fix cloudy pool waters, you are now well-equipped in fixing it by yourself. So go ahead and try it on your cloudy swimming pool.
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