Why Does My Pool Keep Turning Green?

There is no fun in pulling back your pool cover, and then you are faced with the dilemma that your water turned green. Much worst, it smells weird, swampy, and the algae build-up has taken over your pool. It usually happens with stagnant water and without proper maintenance. The only thing to get rid of them is to perform a very thorough cleaning and treating the pool properly to be able to become fresh and clean again.

Why does my pool keep turning green? Pool water that is stagnant for a while will become green because of the algae build-up. Algae are a nasty little creature that grows rapidly, especially during warm and sunny weather. It all comes down to the lack of chlorine present in the water.

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In this article, you will be able to find out why your pool turns green every time and what you should do to avoid it.

What Makes The Pool Green?

The only reason your pool turns green is because of the recurring algae. And it can be a problem for many pool owners because it grows fast and has several contributing factors. Some of the leading causes of pool algae are heat, rain, chemical imbalance, and transfer from one pool to another.

Recurring algae is a Mustard Algae, and it is a yellowish-green color that usually grows on pool floors and walls. Once it is all in there, it will affect the pool water and will eventually turn green. Algae make the water green, and the imbalance of chlorine will let it grow fully.

If there is enough chlorine in the water, algae will pretty much die and won’t start forming. It is why it is important to shock your pool from time to time to ensure it won’t come back. Adjusting the levels of other chemicals can also prevent algae build-up.

Steps For Cleaning A Green Pool

It is never a good sight if you have a green pool instead of a crystal blue pool. It is essential to treat your pool once you see the signs of algae formation. It is because it is never safe and pleasing to look at. Here are some of the steps in cleaning the green pool and some things to consider to make sure you have a healthy and safe pool to swim.

How Green Is Your Pool?

It is essential to know what level of green are we talking about. If it’s too green, some workarounds and solutions might need some considerations. For example, if it is too green, you might need to drain the pool and perform acid-washed instead of shocking.

There are also several cases where it is black instead of green. It is cost-effective to drain the pool and have it acid-washed. Just bear in mind that it costs more money refilling the pool.

If you see at least 6 or 8 inches below the surface, it is most likely that they can be chemically treated. Other than that, you need to drain the pool. Once you establish a pool that needs to be drained or treated chemically, you can go there.

Testing The Water

If the water appears to be the color green, the obvious reason is that there’s a little chlorine in them. And if you decide to shock the pool water, you will only be adding a lot. It is why it is essential to test out the water pH level.

If the pH is very high, the shocking process will only make the pool water cloudy. Try to purchase a high-end test kit because this will be helpful in the long run. The ideal pH should be 7.2 or lower.

When the pH level is too high, adding one gallon of muriatic acid will be enough. Do not worry about adding too much because the pool should be a little acidic for swimming purposes. Test the pH again after 4 hours to see if there’s a change in the level.

Shocking The Pool

Once you have the desired level of pH, which is 7.2, and below, you should use granular chlorine to shock the pool. It is recommended to have a 25-pound container of granular chlorine rather than having those individual 1-pound bags. You will be able to save more money if you opt for the bigger ones. And eventually, you will need chlorine from time to time to make the balance correctly.

Pumping And Filtering

If you have a DE filter, make sure to backwash the DE filter first. Adding DE fresh powder and then shock the pool as explained above. You should make sure that you are running the pump for 24 hours.

For a sand filter, the same process with the DE filter, but the only difference is the backwash time should only be 5 minutes. Lastly, the cartridge filter should be in good condition and properly washed and rinse.

Brushing And Filtration

After the 24 hours of circulation and chemicals check, you will be able to see some results. Your pool should not be green anymore, but it will still be cloudy and need some brushing and filtration for the next day. If the pool is still green after the 24 hours, there might be some mismatched in the chemical balancing.

It is only normal for the cloudiness to go away as for sand filter. It will take a week or so, while for the cartridge filters, it will need more cleaning. If DE filters, there’s a need to do some repair and maintenance.


Overall, the main reason your pool turns green is because of the algae build-up. It is necessary to take immediate action because it is not safe to swim in these kinds of conditions. Not only it looks gross, but it can also be a little difficult and time-consuming to be able to fix the issue.

The process of finding the right blend of chemicals is essential. If you find it challenging to do it yourself, you can always ask for assistance with your pool maintenance service. They will be able to do the hard labor for you.

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