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How to Clean a Green Pool? — Guaranteed Methods for a Spick and Span Swimming Area (2021)

Maintaining a pool is supposed to be a regular responsibility. But one day, you might discover that your swimming pool has suddenly turned green instead of its usual clear color. It’s not an inviting sight and it’s not certainly not good for swimming. 

Today, our experts are going to teach you how to clean a green pool and how to do it fast.

Why Did Your Pool Turn Green? 

If your ground pool is green, the main culprit is usually algae. These are plant spores that grow in stagnant water. It's the chlorophyll released in the process of photosynthesis that turns your pool green.

Algae don’t need much to thrive. With the right temperatures, debris and sun, they can rapidly multiply in a still pool of water. They're so quick that there are cases where pool owners go to bed with clear water and wake up to a green pool. 

There are several reasons for overgrown algae. One of them is having an improper pH balance. Optimal pool water pH levels should be right around 7.5 to 7.8 when measured with a testing kit. If the level is too high, it won’t kill algae and bacteria. It’s also not good if it’s too low as it could cause eye irritation[1].

green pool

A clogged filter may also be why you've seen more algae growth. If your filter is broken, you’re going to have a hard time keeping your pool free of algae spores and debris. And unfortunately, a dirty pool is an even better environment for algae to breed.

And if your area has been seeing a lot of hot, humid weather lately, your pool is going to be more prone to algae. Algae thrive more in hot weather than cold, so you're more likely to see a green pool in summer than in winter. Extra care should be taken in the hotter months.

So, now you understand why you’ve got a green pool on your hands. Our team will now show you how to get rid of it. Here’s how to clean a green pool within 24 hours aside from using a pool vacuum.

How to Clean a Green Pool

To clean your green pool fast (ideally, within 24 hours), our experts listed the following steps:

Clean Existing Debris and Algae

You'll start by removing the larger debris from the pool. You can do this by using a large leaf net or a pool vacuum such as the Aquabot Breeze 4WD. Do not vacuum if you cannot see the bottom of the pool. Vacuuming blindly can lead to a clog in your vacuum, filter, or underground pipes, which is a hassle you do not want. But try to remove as much debris as you can. 

Drain Your Pool

If your pool water is only light green, you could skip this part and treat it chemically. However, this is a faster way of getting your pool cleaned. 

Once the pool is drained, you can now get down there with your brush. If you have an automatic pool cleaning robot, you might be able to save yourself some effort. However, most people don’t have one so, brush, it is. Brushing is a great alternative to clean the bottom of a pool without using a pool vacuum, as well. 

If your pool is already leaning closer to black, it will need to be drained. You might need to give it an acid wash or call a professional to do it. Remember to pay special attention to places where the water doesn't move too much if you choose to do it yourself. For example: under the pool ladder, on the pool steps, and all nooks and crannies at the bottom of the pool

If you have a Pebble Tec or plaster pool, you can use a steel algae brush. However, if you can’t get all the algae out, don’t worry. All of it will be cleared out within the next few steps. 

Reduce pH Level

As our team said before, your green pool is probably partly caused by high pH levels. To reduce them, you’ll first need to learn exactly how high they are with a test. You’ll need a pool testing kit for this next part. 

pool water

If you don’t have a pool test kit, you can buy one for as low as $5 on Amazon. You can search for one that fits within your price range here. Pool test kits basically check the water chemistry. They can show free chlorine level, pH level, bromine, and more. 

Since you have a green pool, it’s pretty obvious that your chlorine and bromine levels are probably quite low. And since you drained the pool and have put it in freshwater, you don't need to check the cyanuric acid (CYA). So, just test the water for pH levels. Remember, good pH levels for a pool should stay between 7.5 to 7.8. 

However, to remove pool algae, you need to make the pH levels even lower. 7.0 to 7.2 should suffice.

To do this, you’ll need to grab that sodium bisulfate. Follow the manufacturer’s instructions concerning how much to add to your pool size and your algae problem's severity. If you're worried about adding too much and reducing the pH level too much, you can add about three-fourths of what is recommended and check the results.

Slowly pour the product into the pools and leave it for at least six hours. Then, come back and check the pH levels. If it’s within the recommended range, you can move on to the next step. 

Looking to do the opposite? Here is how you raise pH levels in a pool.

Shock the Pool

In simple terms, shocking your pool means adding a lot of chlorine to your pool water. And when we say a lot, we mean double or triple your normal amount especially when you are having extreme cloudy pool water. A good way to do this is buying 25 gallons of chlorine and adding three, four, or five gallons at a time. The huge amount of chlorine will work to kill the algae. 

The best and fastest way is to use a shock that contains at least 70% chlorine. If your pool is really green, then you may need to add more shock. But never fear, it's impossible to over shock a pool.

You can get chlorine in both powdered and liquid form, but liquid chlorine works faster if you’re in a hurry. Add more shock at the deep end but don’t neglect the edges either.

Our experts recommend that for even faster results, you can add in a good algaecide to kill off any hardy spores left.

Filter Your Pool

Once you're done shocking, it's time to filter out all the dead algae. From this point on, your pump and pool filter should be kept running until your pool is crystal clear. 

clear blue pool

You’ll need to backwash your filter at intervals to ensure dirt and clumped up algae don’t clog it. How regularly you do this depends on what kind of filter you have: DE or Sand. You won’t have to backwash a sand filter a lot, but it does work a lot slower than the DE filter. 

You might end up having to backwash your DE filter three or four times if you want to clean your pool faster.

Check Pool Purity

We’re back with the pool testing kit. Now, you’ll use it to check whether your pool’s balanced. If it’s not, we recommend lowering the pH levels again or shocking the pool again. 

Once that's done, and you've filtered out the debris till your pool's clear, your pool is once again swimmable. Congrats, you've now learned how to clean a green pool. And to make sure you keep a clear pool, here are a few tips to maintaining it.

How to Maintain Cleanliness of Your Pool

  • Test Your Pool: Use the pool testing kit we mentioned earlier and find a good place close to the pool to store it because you’ll be using it regularly. Ideally, you should test your pool once a day but three to four times a week works, too. That way, you can ensure your pH, free chlorine, and CYA levels are all optimal and can kill spores before they can sprout and add more pool chemicals when needed.

  • well maintained pool
  • Brush and vacuum your pool with excellent robotic pool cleaner at least once a week to keep your pool maintenance up.
  • Check Your Filters and Pumps: Make sure that your filters and pool pump are kept clean and work well so algae spores can't grow in the moving water.
  • Invest in a Pool Cover: Debris and sunlight help algae grow. Keep your pool covered to minimize your pool’s exposure. 

  • FAQ

    What is the fastest way to clean a green pool?

    The fastest way to clean a green pool is to lower the pH level to below 7.2 and then shock the pool with chlorine. Use lots, and then use your pump and filters until it turns clear. 

    How do I get the green out of my pool?

    You can get green algae out of your pool using chlorine shock to kill it and then filter it out. If you want to go the extra mile, you can use a brush to clear out any leftover spores.

    What kills green algae in swimming pools?

    What kills green algae in swimming pools is a combination of low pH levels and high chlorine levels. 


    The problem with algae is that it spreads way too fast. What might be a small issue today might have escalated overnight. Hence, our experts recommend to manage your pool with a weekly maintenance check. That way, you won’t have to spend a whole day dealing with unpleasant algae. 

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