How to Fix a Green Swimming Pool

Kenneth Wilson

It’s a hot summer morning, and you’re ready to start the day with a nice dip in your pool. But as you step outside, you see that your pool has turned green. What a nightmare, eh?

Don't you worry, cause I'm here to help. I'll tell you a couple of effective and proven solutions that you can do to remedy this. But first, it's important to understand what exactly is causing this, what are the implications of green pool, and how you can prevent this from happening again. Let's proceed with the article so you can dive in already!

Why Is Your Pool Green?

If your pool has turned a murky green instead of the normal crystal blue you enjoy, there are three major reasons that may be contributing to discoloration of your pool.


The most common reason for a green pool is an overgrowth of algae. Oftentimes, algae growth is due to a lack of chlorine. If you let your pool’s chlorine levels drop for even a day or so, algae can sneak in extremely quickly- hence the overnight shock! The warmer it is where you live, the faster this will occur. It is vital that you check your pool’s chlorine levels often, to ensure that any algae growth is thoroughly stifled. However, even if you’ve been adamant about keeping your pool’s chlorine levels up, there are still other factors that may cause your pool to go green. 

Firstly, if an overgrowth of algae is the issue, it will likely be growing on the bottom and sides of your pool, and won’t come off unless you really scrub at it. Your water will also look quite murky, and will only get worse as the algae continues to grow. 

Abundance of Pollen

Another potential culprit is an abundance of pollen and/or other small debris that has been carried into your pool by the wind, and is too small to be removed by your regular pool filter. Over time, these particles can build up and discolor your pool. To avoid this build-up, it’s important that you regularly wipe down your pool liner and manually fish out any small debris that you see lurking around your pool.

With pollen and other small debris, it will also likely have settled on the bottom of your pool, and it will also make the water quite murky since there is physical debris floating around. However, unlike algae, these particles should float off the bottom of the pool quite easily if you just wave your hand around- in this case, it is an issue of sediment, not actual growth. 

Oxidizing of Metal

Finally, if you have a significant amount of metal in your pool and shock it, the metals can oxidize and turn your pool green. These metals, such as copper, may become present due to source water, cheap algaecides, or actual metal components of the pool like heater elements. The good thing about this option is that your pool should still be relatively clear, but the bad thing is that the metal-caused green tinge can permanently stain your pool. 

While it’s always a good idea to run a proper test, there are several ways you can tell which factor has caused your pool to go green just by looking at it. 

Finally, if metals are what’s causing your pool to go green, the water should still be quite clear, but with a significant green tinge. If you’re unlucky, there may be green stains on your pool floor or liner. 

Is It Safe To Swim In A Green Pool?

With the sun beating down, you may be tempted to jump in your pool for a quick swim. If it was fine just 24 hours ago, and you swim in green lakes all the time, how dangerous could it be? However, you should proceed with the utmost caution. If your pool has gone green, it may or may not be safe for you to swim in. It depends on both the cause extent of the discoloration.

 If Pool is Green Due to Algae/Pollen

Firstly, a green pool is different from a green lake or ocean because it is a closed body of water, and does not have any sort of natural ecosystem or filtration system (and if it’s green, something is probably wrong with your manmade filtration system). 

If the cause of your pool’s unnatural hue is algae, it’s better to err on the side of caution and avoid taking a dip. While most algae itself is harmless to humans, it can attract bacteria and other amoebas that you don’t want to be anywhere near. The same goes for pollen- there could be anything in the debris that has collected in your pool, and it’s better not to risk it. 

If Pool is Green Due to Metals/ pH Imbalance

If metals and/or a general pH imbalance (provided that there is still a sufficient amount of chlorine to kill any unwanted bacteria) are the cause of the green hue, your pool water is most likely safe to swim in. This isn’t an entirely uncommon occurrence, and even professionals aren’t safe from it- a diving pool at the 2016 Rio Olympics went green. However, you shouldn’t jump in until you’ve thoroughly tested your pool water’s chemical levels. 

How Can You Clear Up A Green Pool?

While a green swimming pool is unsightly and sometimes dangerous, luckily, it can be cleared up quite quickly. In any scenario, it’s best to use a pool test kit both before and after cleaning your pool, to ensure you’ve identified and treated the issue correctly.

Step 1

Test the Chemical Balance

Firstly, if you’ve confirmed that your issue is algae, as mentioned, grab a pool test kit for your local shop to check the chemical levels in your pool. Before you alter any chemicals, however, you should scrub off all the algae already in your pool. Additionally, check your filter to make sure it isn’t clogged, so that it can do its job effectively once you start adding chemicals.

Step 1

Shock Your Pool

To prevent any future algae, your pool’s pH should be between approximately 7 (more on this later), and you should get your chlorine levels above one ppm. To get your water sparkling clean again, you’ll have to shock your water with chlorine. When shocking, make sure you use either liquid chlorine or a granular shock that contains at least 70% chlorine. If your pool is quite murky, you may have to shock it multiple times before it goes back to normal. Add a good-quality algaecide to ensure you treat the root cause, as well. 

Step 1

Clean and Use the Filter

When chemically treating your pool, make sure the filter is running 24/7. Backwash it as needed to prevent any clogs. If your pool water still seems cloudy after shocking it, you likely need to fix the pH- test the chemical levels and adjust as needed. Thanks to the chlorine, it’s probably alkaline. Adding hydrochloric acid may help to neutralize your pool and clear things up. Once your water is nice and blue, make sure you clean your filter once more, and then you can go back to your regular filtering schedule. The final step is to vacuum your pool to get rid of any lingering algae or debris you missed during the first scrub.

Step 1


If pollen is your issue, you should ensure your filter is free of clogs, and backwash it several times to ensure it’s debris-free. Once again, run your filter 24/7 while you take care of your pollen issue. Make sure to skim away as much new pollen near the surface of your pool as you can. However, for the excess build-up of pollen, start by using a water clarifier. The clarifier will coagulate the tiny pollen particles in your pool so that they’re large enough to be picked up by your filtration system. Then, vacuum all the pollen that has already settled at the bottom of your pool. 

Step 1

Maintain your Pool Regularly

Once the pollen is out, test your pool’s chemical levels to ensure everything is in order. While the heavy lifting should be over at this point, unfortunately, you’ll have to continue skimming new pollen from your pool for the entirety of the season to ensure it doesn’t settle. Additionally, double-check that you use a good quality pool cover, and keep it up anytime you aren’t in your pool. This will help prevent pollen from getting in the water at all. Although these tasks can be tedious, they’ll save you from having to go through this entire process all over again. 

Step 1

Use a Sequestrant

Finally, to get rid of metal particles that have turned your pool green, you’ll need to use a sequestrant. Much like a clarifier does with pollen, a sequestrant will join the metal particles together, which will allow them to be flushed out by your filter. Once you’ve done this, you must clean your pool filter to get rid of the particles trapped there. Backwashing it will help, but in this case, it’s probably best to chemically clean it as well to get rid of any lingering metals. 

To ensure you keep your water clean long-term, identify the source of the metals in your water, whether it’s a heater or source water, and adjust your tasks accordingly. For example, if your source water is the issue, you may need to stock up on sequestrants and use them on a regular basis to prevent metals from taking over your pool again. 

How Can You Prevent A Green Pool?

By now, you’ve gone through the tough process of cleaning out your pool. You’ve put time, energy, and money into getting your water back to a beautiful crystal blue. Here’s how you can keep it that way, so you never wake up to gunky green water again. 

Test Chemical Level Regularly

After the pool-cleaning process you’ve gone through, you already know this, but the best way to keep your pool nice and clean is to regularly test its chemical levels, to ensure that both its chlorine and pH levels are where they should be. Ideally, your pool’s chlorine should be between one and three parts per million (ppm), and the pH should be anywhere from 7.2-7.6

Weekly Chlorine Shock

Even if your pool has the proper chemical levels, it’s always a good idea to run a weekly chlorine shock to get rid of any super-strong bacteria. If the algae in your pool also have super strength, add a round of algaecide to your weekly shock to prevent any growth. Likewise, as mentioned, if your source water causes metal particles in your pool, use sequestrant on a weekly basis as well. Once again, also continue skimming any pollen or other bothersome debris to avoid that problem getting out of hand. You may need to do this as often as once or twice a day. 

Backwash Pool Filter

None of these strategies will work, however, if your filtration system is out of whack. Backwash your pool filter regularly, and do so immediately if your water looks even the slightest bit cloudy. To avoid cloudiness altogether, keep track of your pool’s standard pressure gauge reading. Once the pressure becomes 5 to 7 pounds per square inch above normal, it’s time to backwash your filter.

Final Thoughts

If you follow these steps, you’ll be able to maintain a beautiful, clear blue pool that’s the perfect place to spend hot summer days. While pools do require a lot of upkeep, the result is more than worth it.

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Kenneth Wilson
August 6, 2021

Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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