Cloudy pool water is one of the most common problems pool owners experience during the summer. Your pool may look slightly dull one day and become so cloudy that you cannot see the bottom clearly the next.
The cause is not always obvious. Cloudy water can result from unbalanced water chemistry, insufficient chlorine, poor circulation, filtration problems, algae or contaminants introduced by rain and swimmers.
Before adding more pool chemicals, it is important to identify what is causing the cloudiness. Treating the wrong problem may make the water harder to balance and delay the clearing process.
What Causes Cloudy Pool Water?
Cloudy pool water contains tiny particles that are not being properly removed by the filtration system. These particles may come from dirt, pollen, sunscreen, algae, minerals or improperly balanced water.
In many cases, more than one issue is contributing to the problem. For example, heavy pool use can increase chlorine demand while also adding contaminants that the filter must remove.
Here are seven of the most common causes of cloudy pool water.
1. Unbalanced Pool Water Chemistry
Improperly balanced water is one of the most common causes of a cloudy pool.
The main levels to check include:
- Chlorine or bromine
- pH
- Total alkalinity
- Calcium hardness
- Cyanuric acid or stabilizer
High pH can reduce chlorine’s effectiveness and may contribute to scale and cloudy water. Improper alkalinity can make the pH difficult to control, while calcium hardness that is too high may cause calcium to precipitate out of the water.
Test the water before adding chemicals. Home testing can provide a quick reading, but a professional water test may provide a more complete picture when the cause is unclear.
Bremner generally recommends keeping pool pH between 7.4 and 7.6, with 7.2 to 7.8 considered an acceptable range.
2. Low Chlorine or Inadequate Sanitation
Chlorine helps destroy bacteria, algae and other organic contaminants in pool water.
When chlorine levels fall too low, contaminants can build up faster than the sanitation system can manage them. The pool may initially appear dull or hazy before becoming noticeably cloudy or green.
Chlorine demand can increase after:
- A pool party or heavy swimming
- Several hot and sunny days
- Heavy rainfall
- Leaves or organic debris entering the water
- A developing algae problem
- Adding a large amount of fresh water
Do not assume chlorine levels are adequate simply because the pool does not have a strong chlorine smell. Test the water and make adjustments based on the results.
3. Poor Pool Circulation
Balanced water still needs to circulate properly throughout the pool.
Poor circulation can leave areas where sanitizer is not being evenly distributed and debris is not being carried toward the skimmer or main drain. Steps, corners and areas behind ladders are common locations for weak water movement.
Check the following:
- The pool water is at the appropriate operating level
- Skimmer and pump baskets are clear
- Suction and return valves are properly positioned
- Return jets are directing water throughout the pool
- There are no obvious plumbing restrictions
- The pump is operating correctly
If you have a variable-speed pool pump, it may need to operate at a higher speed for part of the day to provide sufficient circulation. The appropriate settings will depend on the pool, plumbing and equipment.
4. A Dirty or Ineffective Pool Filter
Your pool filter removes small particles from the water. When the filter is dirty, clogged or not operating long enough, those particles remain suspended and make the water appear cloudy.
The solution depends on the type of filter:
- Sand filters may need to be backwashed
- Cartridge filters may need to be removed and cleaned
- Diatomaceous earth filters may require backwashing and additional filter media
- Damaged or worn filter components may need repair or replacement
Rather than backwashing on a fixed schedule, check your filter’s pressure gauge. Bremner recommends backwashing when the pressure reaches approximately 10 PSI above the clean running pressure.
If the pressure remains unusually high or low after cleaning, there may be a circulation problem or an issue with the filter itself.
5. Early Algae Growth
A pool does not need to be completely green to have an algae problem.
Cloudiness can be an early warning sign, particularly when it is accompanied by slippery walls, or chlorine levels that are difficult to maintain.
Algae growth is often associated with:
- Low sanitizer levels
- Unbalanced water chemistry
- Poor filtration or circulation
- Warm water
- Organic debris
- Areas of limited water movement
Brush the pool walls, steps and floor to loosen algae and other buildup. Continue filtering the water and clean the filter as needed while the algae is being removed.
After successful algae treatment, the water may turn from green to cloudy white. This is often dead algae suspended in the water, which must then be filtered or vacuumed out. Bremner’s algae-treatment process also recommends cleaning the filter after treatment to remove residual buildup.
6. Heavy Pool Use, Sunscreen and Body Oils
The busiest swimming days can place significant demand on your pool’s water-care and filtration systems.
Swimmers introduce:
- Sunscreen
- Body oils
- Sweat
- Cosmetics
- Dirt
- Grass
- Hair products
- Other organic contaminants
These substances can use up chlorine and create fine particles that are difficult for the filter to remove immediately.
Encouraging swimmers to rinse off before entering the pool can help. After a busy day, remove visible debris, empty the baskets, test the water and confirm that the filtration system is running properly.
7. Rain, Wind and Environmental Debris
A summer storm can quickly change your pool water.
Rain can dilute pool chemicals and affect water balance, while wind may carry pollen, dust, leaves and other organic debris into the pool. If the water level becomes too high, effective surface skimming may also be reduced.
After heavy rain or strong winds:
- Remove leaves and visible debris.
- Empty the skimmer and pump baskets.
- Test the water chemistry. (The pool might need to be shocked after a heavy rain or windstorm)
- Adjust the water level when necessary.
- Confirm that the pump and filter are operating properly.
- Brush and vacuum the pool as required.
Do not automatically add large quantities of chemicals after every storm. Test the water first so you can make the appropriate adjustments.
Why Is My Pool Cloudy After Shocking?
Pool water can sometimes become cloudy after shock treatment.
This may happen because the treatment has destroyed algae or organic material, leaving fine particles suspended in the water. The filtration system then needs time to remove those particles. A clarifer may also help as well to help clear up the water.
Cloudiness after shocking may also be related to:
- Improper water balance
- Insufficient circulation
- A dirty filter
- Dead particles on the floor that will need to vacuumed to waste
Continue circulating and filtering the water, monitor the filter pressure and clean or backwash the filter when necessary. Test the water before adding any additional treatment. The use of a clarifier may help clear the water as well.
Why Is My Pool Cloudy When the Chemicals Are Balanced?
If test results appear normal but the pool remains cloudy, the problem may be mechanical rather than chemical.
Check for:
- A dirty filter
- Restricted water flow
- Blocked baskets
- Incorrect valve positions
- Low pump speed
- Inadequate filtration time
- Damaged filter components
- Fine debris that has not yet been removed
- Early algae in areas with poor circulation
- Dead particles on the floor that will need to vacuumed to waste
A basic test strip may also provide less detail than a comprehensive water analysis. Consider having the water professionally tested if the problem continues. A clarifer may help as well to help clear up the water.
How to Clear Cloudy Pool Water
The correct solution depends on the cause, but this process can help you identify and address the most common issues.
1. Test the Pool Water
Check chlorine, pH, alkalinity, calcium hardness and stabilizer levels. Correct the water balance based on accurate test results.
2. Remove Debris
Skim the surface, vacuum the pool and remove leaves or organic matter. Empty the skimmer and pump baskets. If you have dead algae on the floor, be sure to vacuum that to waste
3. Brush the Pool
Brush the walls, floor, steps, corners and other areas where algae or debris may be collecting.
4. Inspect the Circulation System
Confirm that the pump is properly primed, the valves are open and water is moving through the return jets. If you have a variable speed pump, make sure that its running at a high speed to increase circulation and help clear it up
5. Clean the Filter
Backwash a sand filter when the pressure indicates it is required. Clean cartridge or diatomaceous earth filters according to the manufacturer’s instructions.
6. Address Algae or Low Sanitizer Levels
When testing or visible signs indicate algae or inadequate sanitation, use the appropriate treatment for your pool. Always follow product instructions and avoid combining chemicals unless the products specifically permit it.
7. Allow the Filter Time to Work
Even after the underlying problem has been corrected, the filter may need time to remove fine suspended particles. Monitor the water and filter pressure rather than repeatedly adding more chemicals.
Should You Use Pool Clarifier?
A pool clarifier can help combine very small particles into larger particles that the filter can capture more easily.
However, clarifier should not replace proper water balance, circulation or filtration. If the underlying cause is low chlorine, algae or a malfunctioning filter, clarifier alone will not solve the problem.
Always follow the product instructions. Using too much clarifier can make the pool more difficult to clear.
Can You Swim in a Cloudy Pool?
You should not swim in a pool when the water is so cloudy that you cannot clearly see the bottom or the main drain.
Poor visibility can make it difficult to see a swimmer in distress. Cloudy water may also indicate inadequate sanitation or improper water chemistry.
Wait until:
- The water is clear
- The pool bottom is fully visible
- Sanitizer and pH levels are within the appropriate range
- The filtration and circulation systems are operating correctly
Clear-looking water is not the only measure of pool safety, so always confirm the water chemistry before swimming.
How Long Does It Take to Clear a Cloudy Pool?
The time required depends on the cause and severity of the problem.
A minor filtration or water-balance issue may improve relatively quickly once corrected. A significant algae problem or heavy buildup of suspended particles may take longer because the water must be treated, circulated, filtered and cleaned.
Repeatedly adding products without identifying the cause may extend the process. Proper testing is the best place to begin.
When Should You Call a Pool Professional?
Professional assistance may be needed when:
- The water remains cloudy after testing and correcting the chemistry
- Chlorine levels will not hold
- The pool repeatedly becomes cloudy
- The filter pressure is unusually high or low
- Water flow from the return jets is weak
- The pump is drawing in air
- Algae returns shortly after treatment
- You suspect a pump, filter or underground plumbing problem
A pool professional can assess the water, filtration system and circulation equipment to identify the underlying cause.
Keep Your Pool Water Clear All Summer
Cloudy pool water is usually a sign that something in the pool’s chemistry, sanitation, circulation or filtration needs attention.
Start by testing the water rather than guessing. Remove debris, inspect the equipment and clean the filter before adding multiple treatments. Addressing the actual cause will help clear the water faster and reduce the likelihood that the problem will return.
Bremner Pool & Spa has served pool owners throughout Toronto, Markham and Durham Region since 1981. Contact our team for help with cloudy pool water, equipment problems, algae treatment and other professional pool services.
Frequently Asked Questions
The most common causes include unbalanced water chemistry, low sanitizer levels, poor filtration and inadequate circulation. More than one issue may be affecting the water at the same time.
Chlorine may help when the cloudiness is caused by low sanitation or algae. It will not correct every cause of cloudy water, such as a dirty filter, poor circulation or improper calcium hardness. Test the water before adding chlorine.
Shock treatment may leave dead algae and other fine particles suspended in the water. The filter needs time to remove those particles. Poor circulation, a dirty filter or unbalanced water may also delay the clearing process. If you notice dead algae on the floor, this must be vacuumed with filter in waste mode.
Yes. A dirty or ineffective filter cannot properly remove suspended particles from the water. Check the filter pressure and clean or backwash the filter when required.
Rain can dilute pool chemicals, alter water balance and carry debris into the pool. Test the water and clean the pool after a significant storm rather than automatically adding chemicals.
Do not swim if the bottom of the pool or main drain is not clearly visible. Cloudiness may also indicate inadequate sanitation or unbalanced water chemistry.
Maintain proper water chemistry, keep baskets and filters clean, remove debris promptly by brushing and vacumming regularly, provide sufficient circulation and test the water more frequently will help keep the pool clean and clear.
Guide To Achieving Perfectly Clean And Clear Pool Water
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