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How to Clean a Green Pool: The Complete Guide

Cleaning a Green swimming Pool the right way

Has your pool turned green? Well, don’t worry. It isn’t the end of the world. Sure, it means that you won’t be hopping into the pool right now, but it is a problem that is easy to fix. On this page, we are going to teach you exactly how to clean a green pool.

What causes a green pool?

Before we talk about how to clean a green pool, it is probably worth talking a little bit about why pools turn green in the first place. After all, if you know why your pool is turning green, then it is going to be far easier to prevent it from happening in the future.

green pool

In the vast majority of cases, your pool will have started to turn green because algae and bacteria have started to grow in the water. This is, likely because you have not been using enough sanitizer e.g. bromine or chlorine, in the water. Remember; bromine needs to be added to the water once to twice per week, while chlorine needs to be added at least every couple of days. If you aren’t keeping up with your schedule (and checking sanitizer levels), then it won’t be long before your pool starts to turn green.

If you have been adding sanitizer to the water on a schedule, then the water may be turning green for another reason. For example; the water filters in your pool may have become clogged. In other cases, it may be because the PH levels in the water are wrong. If they are wrong, then any sanitizer you do add to the water is not going to be able to do the job effectively. You can add as much as you want, but it isn’t going to change a thing.

Thankfully, it doesn’t matter too much about why your pool is green. Dealing with the issue and cleaning the green away is going to be fairly fast. Although, of course, it does help to know why your pool is green in the first place. It is going to make troubleshooting a whole lot easier for you.

Throughout the rest of this page, we are going to teach you how to clean your green pool. If you follow this advice, you will be able to get your pool nice and blue in next-to-no time at all. You will also have information on how you can prevent the issue from occurring later on.

Determining whether your pool needs to be drained

Did you know that in the vast majority of cases, you don’t have to drain your pool at all? If you have managed to catch the problem early, and the water hasn’t turned black, then it should be fine to just throw some chemicals in there (using our advice, don’t just throw chemicals in there) and your pool should clear up on its own.

If it is difficult to see the bottom of the pool, then it is probably going to be easier for you to drain the water completely. You can then climb into the drained pool and give everything a good scrub down with a quality pool wash. Of course, since this is a process that is going to take an incredibly long time, most people will probably want a slightly different way to tackle the problem. In most cases, draining the pool should be an absolute last resort.

If you do drain your pool, then make sure that when you fill it up, you follow the correct processes i.e. adding the right amount of chlorine, and properly filtering the pool. If you do not do this, then your pool will be green again in mere weeks.

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Bringing your PH levels to the right point

Since you own a pool, we are going to hope that you have a PH testing kit to hand. If you don’t, pick up a few of them. They are cheap, and it is likely that the whole reason you have a green pool is that you were not checking the PH levels regularly.

Follow the instructions on the PH kit. You will want a PH level of 7.5. If it is not at this point, then you are going to need to reduce the acidity of the pool. Thankfully, this is another simple problem for you to deal with. You will need to get your hands on some sodium bisulfate, though. Again, this is something that you should own if you have a pool. If you don’t own any sodium bisulfate, then it is likely that your pool has been getting a little bit too acidic for a while.

The exact process that you add the sodium bisulfate to the pool will be dependent on the acidity levels. It will also be dependent on the product that you have purchased. Read the manual for the product.

Remember; this is not going to balance out the PH right away. It will need to stay in the water for a good few hours.

Killing off the algae and bacteria

Now you have brought PH levels in line, it is time to move onto the next part of the process when it comes to how to clean a green pool. This is killing off everything that is living in the pool. This stage of the process is NOT going to get rid of the algae, but it is going to kill it. This makes it easier to flush away later on.

The process here is known as ‘shocking’ the water. For this, you are going to need to have liquid chlorine…and a LOT of it! This is a process which may take many days. It is going to be highly dependent on how green your pool is.

Start by adding a few gallons of liquid chlorine to the pool and then leaving it for a day or so. If this doesn’t work, then add a little bit more. Keep doing this each day. Eventually, the water will turn white or a little bit cloudy. Basically, the green will have virtually subsided. There may be a little bit of green here and there, but it is going to be nothing to worry about. What is important here is that you have killed all the algae and bacteria. This means that you can move onto the next stage of the process.

Clean your filter

Now is the point where we start to clean up your pool properly. For this, we are going to need to filter everything out of your pool which doesn’t need to be there. For this, you will need to ensure that your filters are not clogged. If they are, then this is not going to work.

We are not going to go into the process of unclogging your filters here. They will all work in slightly different ways e.g. some filters may require backwashing, while others will not. We suggest that you read the manual for your filters to work out what you need to do.

In some cases, your filters will be so clogged that they are beyond cleaning. You may actually find it a lot more beneficial to remove and replace the filters completely.

Switch on the pump

Once the filters are clean, turn on the pool pump. This will start to filter out all of the residues in the pool. It won’t get all of it. It should get most of it. Don’t worry. We are going to get rid of the cloudiness in the next step. For now, leave the pump and filters running for a while. Some people may leave everything working overnight. Your main goal here is to reduce the cloudiness as much as possible. If there was a lot of grime inside of the pool, then you may need to clean your filters again.

Cleaning up the last of it

For the final part of the process, you will need two chemical compositions:

  • Flocculent
  • Algaecide

The purpose of the flocculent is to allow all of the particles in the water that couldn’t be filtered out to start to clump together. This will allow them to be caught in the filters. This will stop the water from being cloudy. Basically, that is the last step of the process to ensure that your water is nice and clean.

The job of the algaecide is to eliminate any algae spores that may still be in the pool. There shouldn’t be if you followed this guide on how to clean a green pool to the letter, but better to be safe than sorry.


We know that cleaning a green pool can be quite a long and convoluted process. However, the great thing is that if you put the effort in, you can actually prevent the issue from happening in the first place. Make sure you keep your filters clean. Make sure that you regularly check PH levels of the water. Make sure you use your sanitizer. You may even want to sprinkle in a bit of algaecide on occasion. All of this will help contribute to beautiful, clear water.

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