Cloudy Pool Water

Cloudy pool water can happen overnight and when it does it can be difficult and time consuming to diagnose and remedy, but it doesn't need to be. There is nothing more disheartening than going for a swim with family or inviting friends over for a swim only to find that your pool has clouded up unexpectedly. The good news is that there is always an explanation and after reading this page you will have a better understanding why it happens.

cloudy pool water

Since pool water can become cloudy for many reasons you may need to spend a bit of time up front figuring out what exactly is causing the problem. It may take some time initially but as you learn your pool you'll figure out ways to not only fix it, but prevent it from happening in the first place. Keep in mind that every minute you spend learning about your pool will make it easier to maintain and diagnose in the future. 

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What Causes Cloudy Pool Water?

Every pool is different and it would be impossible to go over every possible cause of cloudy pool water. We will however go over the most common problems for salt water pool owners and regular pool owners and then we'll go over how to fix and prevent some basic problems that can occur. The most common reasons your swimming pool water is cloudy can be categorized into two main categories; chemistry and sanitation or filtration and circulation.

The goal should always be to first diagnose the problem and fix it with as little chemicals as possible, if they are even necessary in the first place. As a general rule you should always start using less and never add any product based on a hunch unless you really know your pool. A lot of pool problems including cloudy water is simply caused by too many chemicals being added to the water over time. If you own a salt water pool you will likely experience less chemistry related problems versus a regular chemical chlorine pool.

Pool Chemistry and Sanitation

The number one cause of cloudy pool water is inconsistent chlorination or low free chlorine. If you don't maintain a steady level of free chlorine by producing it through your chlorine generator, utilizing the built in super chlorinate feature or a chlorine dispenser you could run into all sorts of problems.

It speaks to the importance of purchasing a quality pool test kit so you can keep an eye on your pool's chemistry. It means you won't have to rely on guesswork, inconsistent pool store analysis or low quality strips with inaccurate results.  

pool chemistry

Chemistry Related Problems that Cause Cloudy Water

  • Inconsistent or inadequate chlorination.
  • The pool shock was used incorrectly or added simultaneously with calcium chloride. Never add chemicals at the same time, always allow one chemical to dissipate before adding another. 
  • An overdose of chemical increasers including; alkalinity, pH and calcium.
  • Langelier Saturation Index is too high. 
  • Iron or manganese in the water.
  • An overdoes of stain and scale inhibitors, flocculant or foamy algaecide.
  • Using minerals or catalysts without sufficient shocking.
  • Paint, oil, tree sap, dust, rainwater and other environmental contaminants. 
  • An excess of people, pee, lotion and other biological waste. 
  • Pool water is more than 5 years old.

Pool Filtration and Circulation

Aside from inconsistent chlorination or low chlorine levels, the most common culprit causing cloudy pool water is pool algae typically caused by poor sanitation and circulation. If your pool is green and cloudy you can almost be sure that you have an algae issue that needs to be dealt with.  

In addition to living algae you may end up with cloudy water from dead algae that can be very difficult to remove especially if you are using a sand or cartridge filter. It will appear as grey or white cloudiness usually after using an algaecide or shock. 

pool circulation

Filtration Related Problems that Cause Cloudy Water

  • Algae alive or dead.
  • Pool pump and filter system are not running for long enough intervals.
  • Pump is creating too much pressure for an undersized filter, usually a sand filter.
  • The pump is not sized properly and isn't creating enough pressure to filter adequately and complete adequate water turnover.
  • The pool filter is dirty, blocked, damaged, missing filter media or parts, not set properly, or backwashed improperly.
  • Plumbing is damaged, blocked, too narrow or a valve is closed off. 

How to Fix Cloudy Pool Water

It isn't always easy to diagnose cloudy pool water but now that you know the most common culprits you can hopefully fix the problem without adding any sanitizer or chemicals. It's also possible that all you need is to increase chlorine production on your chlorine generator or increase the amount of time your system is running throughout the day. If you don't own a salt water pool system you may just simply need to add more chlorine during times of high bather load, increased rainfall or extreme heat.

1. Test and Correct the Chemistry

The very first thing you should do is test your water using a quality pool test kit or take it to a local pool store. It is very common for test strips and even local pool stores to give unreliable test results so it's a good idea to double check. If you are a salt water pool owner we recommend an all in one kit that includes a reliable saline test. The money you spend on a good drop test pool kit is going to be worth every penny down the road. 

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Test for 10 pool chemistry parameters including; salt, chlorine, pH, alkalinity and calcium instantly and digitally.

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pool test kit

2. Clear up the Pool Water 

It's time to look at the results of the test and adjust chemical levels as needed. It's a good time to read through our pool maintenance information to make sure you are within the recommended ranges for; salinity, free chlorine, pH, alkalinity and calcium hardness. As you work on getting the core chemicals balanced you may find that any of the following options will give your pool a boost towards getting back to normal.


A low level of free available chlorine could be causing the cloudy water. If there is more than 0.3 ppm difference between total available chlorine and free available chlorine it means that you have high chloramines and a shock will be beneficial. A good pool shock will kill chloramines and free up the beneficial chlorine in your pool. Keep in mind that a shock may temporarily cloud your pool so be sure to keep your filtration running until it has cleared up. 

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If you have determined that your pool chemistry is balanced including acceptable free chlorine levels, your next option is to try a pool water clarifier. Pool clarifiers are a coagulant that clumps tiny particles together into bigger particles so they have a better chance of being filtered out. If you use a clarifier keep your filter system running and clean at all times and your filter may require a backwash or cleaning during the process. 


A flocculant or floc for short is a great product if you want to clear your pool fast but it will require some time and effort on your part. It's similar to how a clarifier works by collecting small particles together but instead of them being filtered out, they are so large and heavy that they sink to the bottom of the pool. The particles that have collected at the bottom of your pool need to be vacuumed out with your pool vacuum set to "waste" or "backwash". This will avoid passing the debris through your pool filter system where it can get clogged. 

HTH Pool Flocculant to Clear Cloudy Water Fast

Clear up cloudy water fast but only for pools with vacuums that take settled materials directly to waste. 

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pool floc

3. Maintain a Clean Filter System

It's important to ensure that your filter system is working properly and stays clean especially throughout the cleaning process. If you use a shock or floc the filter can get clogged very quickly so make sure to keep it as clean and clear as possible. A good working filter system is key to keeping pool water clear so it's always good practice to keep the filter clean and your system running at least two cycles of 8 hours every day.  

4. Purchase a Quality Pool Cleaner

A quality pool cleaner in combination with a properly maintained filter system will work wonders for keeping your pool clean and free of debris. The added benefit of a good cleaner is you will likely experience cloudy water significantly less as the cleaner removes impurities from the pool water, even after floccing. A robotic pool cleaner that works independently from the pool system will ensure that the suction power is always at peak efficiency and it isn't compromising the filter system.

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