7 Most Common Causes of Cloudy Pool Water (and How to Fix It)

You have a great swimming pool and love to take a morning dip or just relax beside it in the evening. However, there’s an issue: you notice the water isn’t clear. It is slightly cloudy or straight-up milky. And as time passes, it doesn’t get any clearer. What could be causing this?

The common causes of cloudy pool water include very high or low pH, excessive undissolved calcium, young algae, floating debris, clogged filter, and nonfunctional chlorinator. By balancing the pH and adjusting pool chemicals, you can get back your pool’s clarity.

However, each cause has a somewhat different solution, which is why this post is as long as it is. Make sure to read the article to understand how to spot the exact cause of cloudiness and fix it as cheaply as possible.

1. The pH Is Too High

High pH is the first and the greatest reason why your pool water is cloudy. Keep in mind that having high pH means that calcium is not dissolving in the water., which can cause a cloudy appearance. Please note that translucent appearance isn’t bad just because the water doesn’t seem aesthetic or appealing to swim in, but because the presence of high amounts of calcium can be bad for the water itself.

Its concentrated presence is a cause for concern because the water becomes cloudy. Moreover, this cloudiness signifies that the water will leave deposits (learn more about hard water) and clog your filter panel and circulation plumbing. Take this as a warning sign and balance your water’s pH as soon as possible.

2. The pH Is Too Low

The second reason for cloudy pool water is, ironically, too low of a pH. If the water’s pH isn’t properly balanced and gets too low, it affects how chlorine reacts with water. Chlorine reacts very fast with water if the pH is too high, and such reactiveness leads to excessive amounts of chloramine. Chloramine is a chemical that wouldn’t be present in such abundance if chlorine reacted slowly. 

Its presence is an issue because, just like calcium, it also makes the water cloudy. This cloudiness is a lot more translucent. Opaqueness and translucence can be used to indicate whether the water is cloudy because of hardness (calcium/high pH) or due to chloramine (low pH). Still, it is advisable to use a pH testing mechanism to be certain whether the cloudiness is because of high pH or low pH. In some instances, you might discover that it has nothing to do with PH at all.

Adding pool acid or alkalis is how you will balance the pH. If the pH is too low, you can add acidic pool chemicals and retest the water. If the pH is too high, you can add more alkaline pool chemicals and retest the water—Retest after each adjustment to ensure that the pool pH is at the recommended levels.

3. Improper Alkalinity Levels

Remember that it is nearly impossible for the pool water’s pH to be off the recommended range without the pool’s alkalinity being affected. This, however, presents a whole different problem. If your pool’s alkalinity is too high, you will likely have a cloudy layer atop your pool.

Whether this is the causal reason or is a symptom isn’t really clear, though; treating it as a cause can help you offset the cloudiness problem. If you balance the alkalinity, the overall cloudiness goes down. Whether this is because you are treating the corresponding pH or whether the alkalinity itself is the problem shouldn’t be your concern. As long as you balance pH first and double-check and balance alkalinity, you’ll have cleared your pool.

Of course, there can be other causes, so don’t go testing your pool just yet. Depending on the water supply, your pool’s alkalinity might get messed up because of the pH, or its pH might get messed up because of the alkalinity.

4. High Calcium Presence

You must just consider the pH for now because the next cause ties into that. Remember that we covered pH increase as a contributor to water harness (more undissolved calcium). Well, as long as there’s more undissolved calcium in the pool (regardless of pH), your pool will be cloudy. In other words, high calcium hardness is another reason your pool water can get cloudy because undissolved calcium can form a translucent layer of whiteness, which can be perceived as cloudy, especially when it turns opaque.

As mentioned above, this is a problem not just because the water becomes cloudy but because the water hardness can lead to build-up in the pool’s finer plumbing, clogging the filter. This in itself can be the reason your pool water is cloudy. To offset this, make sure you are using the right kind of calcium and treating the hardness so the water can dissolve calcium. Lowering the levels of calcium can help as well.

A quicker remedy is adding chemicals that can accelerate the dissolving of calcium. Once again, it all goes back to the pH and alkalinity. If the pH is not too high, the calcium can dissolve better; lowering the pH using the right acids can be a great road to that if you haven’t truly saturated the water’s solubility by adding too much calcium. If you feel like more than pH, your excessive dumping of calcium is to blame; draining some water and adding more might help. Please remember to retest the pH after you refill the pool.

5. Accumulated Phosphates and Bromine

If accumulated phosphates and bromine levels rise beyond a specific point, your pool water will start getting cloudy. Of course, this cloudiness will not be the same type as the calcium hardness variety. That’s because the water will not be too cloudy and will require some squinting or low levels of sunlight to be noticed.

It is easy to miss this milkiness if you live in a place with plenty of harsh sunlight. Do not treat this the same way you would treat calcium hardness because in doing so, you might end up with an imbalanced Ph. Try to deal with it by handling chemical stabilization as a problem in itself without considering the pH and alkalinity in the equation. Once you’ve stabilized the chemicals, you can return to pH testing and ensure that everything is as it should be.

6. Filter Problems

Improper filtration can be another reason your pool water is cloudy because if the water is not being filtered properly, it might have accumulated debris. If the debris is fine enough as white sand, it manifests in the form of milky clouds. This is especially true if the water is being circulated fast enough.

If you turn off the circulation for a while and debris settles to the pool bed, you can see that this is the issue. However, trying a pool pH test before doing the debris test is practical because that is more likely to be the culprit than floating microscopic debris. If you test your pool’s chemical balance and it seems to be at the right levels, and you still manage to notice some whiteness in the pool water, chances are quite high that there is floating debris. 

It is also worth noting that if you test the chemicals and the pH levels are fine, but the chlorinator is not working properly, you might have the problem of early stages of algae at your hand. Having algae in the pool is, of course, no one’s idea of an ideal situation, and one will need to drain out the pool and use chemicals to get rid of algae.

You should, in this instance, clean the pool and fill the water back up. Keep in mind that you cannot see an alga. Algae are noticeable when they form colonies. Algae in themselves are microscopic, and only when they start propagating will you first notice some levels of cloudiness.

If the pool cloudiness is not exactly white and borders on yellow, you have the problem of early-stage algae. Treating it as a certainty instead of as a possibility is the best way to deal with this. As long as you use the right chemicals to clean your water and get rid of algae by shocking the pool, the problem will no longer persist.

7. Increased Ammonia Levels

Higher levels of ammonia can also cause cloudiness, though this cloudiness makes the water more opaque. And there is not a hint of yellowish or white clouds, but simply higher color saturation of the water itself. In other words, you will see more blue in your water and less clarity.

To fix this, simply add more chlorine. The more chlorine you add, the more instant clarity you will witness in your pool, especially if you turn the circulation off before doing this. However, to eliminate the pool’s cloudiness, you have to be strategic and go from the lowest cost solution to the highest cost solution, making it more economical to get rid of cloudy water without trying higher cost solutions that you might not have needed in the first place. 

How to Fix a Cloudy Swimming Pool? 6 Steps to Take

If the problem was the kind that could be solved by simply balancing a few chemicals, there’s no point in replacing the filter panel. Let’s go through the steps that you need to take to get rid of cloudy water in your swimming pool in the sequence of ascending budget demands.

1. Test the pH Levels

It costs you the least to test your pool water using a digital testing kit because you will not be guessing and throwing random solutions at the metaphorical wall. By recognizing the most likely problem and confirming it using a water testing kit, you make sure that you do not spend any money on extra chlorine, ammonia, or new filter panels because none of those might be needed if the problem has to do with the pool’s pH levels.

2. Classify High pH, Low pH, or no pH

Once you finish the test, you have to categorize the problem as high pH levels or low pH levels if the pH is not within the pool’s recommended range. Of course, there’s a small chance that the pH is in the recommended range, yet the water is still cloudy. This brings up the question of what the recommended range is. 

While the other factors vary depending on where your pool is, the actual pH levels recommended for pool water do not change regardless of where you are or which season of the year it is. Your pool water has to have a pH between 7.2 and 8.0 to be safe to swim in for extended periods, but for the water to have the ideal clarity of an aesthetic swimming pool, you need the pH to be between 7.2 and 7.4.

If your testing kit result shows a pH higher than 7.6, you will need to lower the pH by adding alkaline chemicals. On the other hand, if the pH is below 7.2, you will need to increase the pool water’s acidity using muriatic acid. You should consider that if the pH is too low, then the problem could also be because of high amounts of ammonia. 

3. Consider Recent Ammonia Use

Here, you will need to ask yourself the question of whether you have recently dumped a lot of ammonia in your water, and if that’s the case, simply adding excessive amounts of chlorine can clear the water. That said, you have to be cautious that you’re not going overboard and overcorrecting. Adding chlorine is also a great way to get rid of microscopic life forms. You might also want to concentrate efforts on getting rid of young algae or bacteria in the process. 

Using high-speed circulation and a fresh filter panel can help with this, though these are steps within themselves that you need to undertake if the water’s pH is fine and barely above or below the recommended limit while the cloudiness is too high. If the water is too cloudy, while the pH levels aren’t that off the recommended range, it could be due to two different causes, resulting in the same symptom. That’s when you need to treat or test for debris.

To test whether debris is responsible for the cloudiness of the water, you need to turn off the circulation. Let the water sit for a few minutes and see if any debris settles at the bottom of the pool. If the pool water starts to get clear at the surface, then the chances are that there is debris in the water. Simply waiting for five to ten minutes and then taking a bucket out of the pool’s surface can be a great test for whether the cloudiness has any correlation with debris.

If the bucket comes off relatively clear, then the chances are that the debris starting to settle at the bottom is responsible for the cloudiness. If the water is just as cloudy in the bucket as it is in the pool, the chances are that there is a different explanation. In that case, you need to get to the next stage of your cloudiness clearing mission.

4. Lower Calcium Levels

If the pH is just a little higher, but the cloudiness is too high, then the chances are that you’ve added too much calcium, and the pH levels being a little off is only accelerating the impact of calcium on the water. You can simply correct the calcium hardness levels to fix this problem. And to fix calcium hardness, you need to drain some of the water and add more fresh water from outside the pool’s current circulation. 

This dilutes the level of calcium in the water and, to some degree, helps with the pH. Keep in mind that you will need to retest the pH levels and adjust the pool chemicals. Once you add fresh water Replacing your filter at this point would also be necessary, regardless of whether there is debris in the water filter or simply high calcium presence; chances are the filter requires backwashing, and the filtering agent needs replacement. 

5. Replace Filter Panel and Backwash Filter

That’s because whether it is a causal problem or not, the filter has been compromised. If the filter were working properly, these issues would not be as apparent. If you have not recently placed the filter, it’s good to backwash and replace the filtering agent just to be on the safe side.

Next, you need to check the chlorinator and make sure that it is working properly. If the chlorinator is not releasing the right amount of chlorine, there will be bromine accumulation that makes the water cloudy. Since this is a relatively higher-cost solution, you have to be very careful about implementing it. Do not implement it right away and let the pool run for a few weeks. 

If it starts getting cloudy again, the chances are that the chlorinator is the culprit. Of course, this can require draining water, and some homeowners might not want to incur that cost. But replacing a chlorinator that is working properly costs a lot more, especially if your swimming pool is not Olympic-size and is a regular family swimming pool.

6. Scrub and Vacuum the Pool

Finally, you should check for foreign particles and mineral deposits. Scrubbing your pool and vacuuming it can get rid of particles that could have accumulated because of higher calcium hardness or a faulty filter. This is a final step that you need to take regardless of why your pool water was cloudy because it is just safer. You need to vacuum up the pool now and then anyway, and to do it right after you have cleared out the water is a great way to make sure that your pool doesn’t get cloudy again.

Final Thoughts

A pool’s clarity is a great contributor to its beauty and also a signifier for water safety. To ensure that your pool is beautiful and healthy to swim in, make sure its pH remains balanced and filter, clog-free. Using a pool chemical kit, chlorine, and regular skimming are all recommended for this.

Jed Arnold

Jed spent every year from the ages of 15 - 22 as a Lifeguard (Red Cross) and ages of 17 - 22 as a Certified Pool Operator (CPO). Between working for over a dozen facilities and owning a pool, he carries over a decade of pool experience.

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