How to Clean a Green Pool Fast

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USA Pool Direct clean green pool fast

How To Clean A Green Pool Fast?

Just Imagine that feeling of accomplishment you’re going to have! After reading this article you’re going to be a master at getting the green out of your pool. No longer will you spend money or waste time with pool cleaners. Here at USA Pool Direct, we want to teach you everything you’ll need to properly maintain a pool. Today we are going to start with getting the green out of your pool.

Why Is My Pool Green?

First, you should know the only thing that can turn pool water green is Algae. Algae can grow for a handful of reasons: when the pool is lacking in circulation, the water is warmer than normal, or if the chemicals are out of balance. Sometimes, algae can grow during the winter and is often found when you go to open up for the summer. When you find it? You may be asking yourself if it is even safe?

Is it Safe to Swim in Green Pool Water?

If you find yourself asking yourself, “Can this green pool water make me sick?” Please know that the answer is yes. Algae in a pool is a much higher health risk than algae in natural bodies of water. In a pool, algae can also indicate the existence of dangerous bacteria. You need to make sure that your pool gets back to a stable chlorine level before even thinking about getting in. Below we will walk you through the steps to make your pool swimmable again.

USA Pool Direct clean green pool fast

How to Get Rid of Green Algae in a Pool

The only way to clean a green pool fast is to kill the algae that have bloomed in the water. This can be done by shocking your pool with high levels of chlorine. The experts at Trouble Free Pool coined the S.L.A.M. method (Shock Level And Maintain). The basic premise is to determine what level of shock you would need to kill all the algae, and then maintain this level until the pool is completely clear again. If you don’t know, shock is when you add three to five times the normal amount of chlorine to kill the bacteria fast. Then Maintaining is the process of waiting and checking all your other levels until it’s safe again. If you would like to learn more from the experts at Trouble Free Pool then check them out at Trouble Free Pool

Remove Debris and Brush the Pool

Depending on how long the pool has been stagnant, there may be a lot of debris that needs to be removed before any other steps can be taken. Leaving debris in the pool can mess up your chemical testing and make the shock process less effective. Make sure to also brush as much debris and algae buildup as you can off the pool sides before starting.

Test the Water

First, you will want to test your pool water to determine exactly how you will get it back into equilibrium. Anytime that chlorine drops below 1 ppm it can lead to algae growth. The ideal level for a pool is 2ppm. The experts recommend a FAS-DPD test kit that will be able to handle the larger than the normal range of chlorine.

Balance the Pool Chemistry

The three key measurements that you need to make sure are in the right ranges are pH, cyanuric acid (CYA), and free chlorine. pH needs to be between 7.5 and 7.8, which is higher than usual but will help the shock treatment be effective. To balance your pH, you can use either a pH increaser or pH decreaser. 

Your CYA levels should be between 30 – 60 ppm. CYA acts as a stabilizer for chlorine. This means that it needs to be in this range so that the chlorine can work effectively and kill the algae. If your CYA is too low, you can add more to get to the correct levels. If your CYA is too high, the only way to lower it is to drain the pool and add fresh water.

Finally, you will need the free chlorine levels in the pool. Now that the pH and CYA are in the right ranges and you have the measurements of free chlorine, you can shock your pool.

How to Shock a Pool that is Green

Treat the Water with Shock

Consult the chart from Trouble Free Pool in order to determine what shock level the pool will need to reach.

USA Pool Direct clean a green pool fast
Photo Source: Trouble Free Pool

You can then also use Trouble Free Pool’s Pool Math Calculator to determine how much liquid chlorine you will need to add to reach your shock level.

Once you know how much liquid chlorine you need to shock your pool, you should walk around the perimeter of the pool pouring it in slowly. The S.L.A.M. method now comes into play because you will test your pool every few hours to make sure that the chlorine level stays at your shock level. Algae consume chlorine, so you will need to consistently replenish and maintain the shock level in order to kill all of the algae in your pool. As the algae slowly die, the pool will turn from a green color to a cloudy white and eventually to crystal clear. You will need to maintain your chlorine levels until the water is crystal clear.

Vacuum and Run the Filter After

The shocking process can take multiple days depending on the algae in your pool. For this reason, you will need to keep up with vacuuming and brushing your pool each day. Brush the walls of the pool to dislodge any algae that you missed with the first brushing. Vacuum the bottom to get rid of all the dead algae that have settled on the bottom.

Deep Clean Your Filter 

Make sure that you clean your pool filter on the first day of the shock process. Algae can also build up in the filter and cause regrowth after you think you have killed it all. You should be running your filter throughout the entire S.L.A.M. process. If your shock process takes multiple days, then make sure to clean your filter every day to remove the buildup from the dead algae. If you need more help on deep cleaning your filter than you should check out our pool filter blog. Visit How To Backwash a Pool Filter.

Overnight Chlorine Loss Test (OCLT)

Once your water is crystal clear, you may think that you are done. This is where many people go wrong and have green water again within a matter of days. The only way to know that you have killed all of the algae in your pool is to perform an overnight chlorine loss test. Two factors will cause the chlorine in your pool to lower: direct sunlight (UV rays) and algae. By performing this test overnight, you are eliminating the sunlight factor to determine if there are any remaining algae in the water.

Record your free chlorine test in the evening after the sun has set. Before the sunrise, test the levels again. If the free chlorine has stayed the same or dropped by less than 1, you have passed the test. If not, then you will need to keep S.L.A.M.-ing.

If you are done, you will need to let chlorine levels drop down to your pool’s normal range before letting anyone swim. It would be good to keep checking all of the chemical levels at this point. Sometimes shocking can throw the pool out of equilibrium, so make sure your chemistry is balanced before letting anyone swim.


If you have any more questions about fixing your green pool water, this video by our friends at Swim University is very detailed and helpful.

Green Pool Water Troubleshooting

Why is My Pool Water Still Green After Shocking?

Why is My Pool Water Still Green After Shocking? There could be many explanations for your pool remaining green after multiple shocking efforts. Our List could help you find out why. 

  • Your pool chemicals are not balanced and therefore the chlorine will not be able to work effectively. 
    • For example, if the pH is too high (8.0 or higher), then the chlorine will be 80% ineffective and unable to kill the algae. Make sure that all of your pool chemicals are balanced. 
  • Some people only follow the shock dosage provided on the label of the container, and this is not enough for the S.L.A.M. method. 
    • Follow our instructions above to figure out how much shock you will need. Killing algae takes much more chlorine than regular weekly shock treatment.
  • If you are using Algaecide, just know it will not clear a green pool. It is more effective as a preventative measure than as a treatment to kill algae.
    • Use algaecide regularly once your pool is clear again to make sure you do not have another algae bloom.
  • Make sure that your filter is running all day and all night during the S.L.A.M. process. Some people make the mistake of only running their filter on their regular schedule. 
    • A crucial part of killing the algae is making sure that there is a constant circulation of the pool water. You also may need to replace your filter media if it is not working efficiently.
    •  It would also be smart to make sure you have a large enough filter to maintain your pool. If a filter is too small, it will not be able to effectively filter all the water which could lead to recurring algae blooms. 

If the Shock Treatment Turned Your Water Green

If you have green pool water after shocking your pool, then you may have too much copper in your water. You may have copper naturally present in your water source or it could be coming from the plumbing. You will need a chelating agent to clear up your water. Once you have treated your water with this, test your other chemicals again to make sure none of them were thrown out of balance.

Quick Dos And Donts List

  • For the Sake of the pool, please do not rush! if you follow our guide and use the right kind of supplies you can have a clear pool in 24-48 hours.
  • Do Not Use Bleach or Baking Soda as a replacement for proper chlorine or chemicals. Not only are these not as strong, but they can do major damage to your pool and equipment.  
  • Please do realize, all these Methods we have given you in this blog will work for above and inground pools. 
  • Please Feel Free to contact our experts at USA Pool Direct if you have any questions or concerns cleaning your pool at 855-737-8983. 

Now you have all the tools and knowledge to clean your green pool fast, you are the expert. Never again will you be caught calling a pool cleaner and spending too much.  If you have any further questions regarding algae, chemical balancing, or pool maintenance at large, please feel free to comment below or contact our pool experts at 855-737-8983. 



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