How to Turn Cloudy Pool Water From Green to Blue

If your pool water is cloudy or a sick dark color, and you’re looking for tips on how to turn it from green to blue, then this is the post for you!

For years, I’ve had a love / hate relationship with my pool. I love it in the middle of the summer when it’s 100 degrees outside and I want a nice, cool place to float around all afternoon. But I hate it when I pull the cover off every spring only to find a puke-colored, army-green swamp where my crystal blue water used to be.

Believe me – I know how desperate you feel when your pool looks like this and you fear it will never be suitable for human life ever again! And the amount of money you can spend only to literally accomplish nothing can be ridiculous!

Don’t think so? Here’s an embarrassing story: The first spring after we installed our pool, we pulled the cover off only to find the water had turned a terribly dark green color. Trip after trip to the pool supply store, we tried literally everything they recommended with no success. We even called a “pool cleaning service” to get a quote, but the price they asked was so insane we said forget it!

I finally gave up and actually emptied all of the water from our pool in hopes that I could “start over”. Yup … 20,000 gallons of water and all the chemicals emptied into the storm drain – what a complete waste of time and money! And you want to know what happened next? As soon as I filled the pool back up with water, the green color returned and we were right back to where we started. How frustrating!

So why was this happening? Why was I having such a rough start to opening our pool? It was because I didn’t understand why my pool water was green in the first place, and what I really needed to do in order to turn it back to crystal clear blue. I didn’t invest any time into understanding the simple chemistry experiment a swimming pool is. And as a result, I probably literally threw hundreds of dollars down the drain.

You see, when you’ve got green pool water, you’ve most likely got a problem with algae. Algae is great for swamps, but not so great for backyard pools. And the sooner you understand how to properly get rid of it, the sooner you and your family can sit back on an inflatable raft and enjoy your beautiful blue swimming pool again.

That’s why I’ve written this article. After living in two different houses with swimming pools (one above ground and the other in-ground), please allow me to help you fight your pool water problem head-on by turning it from green to blue, and saving some money in the process!

1- Make sure the pump is running smoothly

First things first: As soon as you open your pool in the spring, make absolutely certain that your pump is running smoothly.

If the pump isn’t circulating the flow of your water properly, nothing else we do in this article will matter. Why is that? Because in order for the green water to travel through your pool filter and get “filtered”, it has to circulate from your pool to the filter and back. Therefore: If there’s no circulation, then there can be no filtration!

So how will you know if the pump is working properly? Try these two ways:

• Put your hand in the pool water in front of a jet. Do you feel the pressure of water blasting out? Or is the pressure weak? Or nothing at all?
• If your filter or pump has a pressure gauge on it, check that it is not reading zero or close to zero.

No pressure at the jets or a near zero reading on the pressure gauge most likely indicates that your circulation system is clogged some place. That’s a problem! Here’s a few things to try to solve it:

1. Start by cleaning out all the junk (leaves, cotton wood, etc.) from the skimmer baskets.
2. If your pump has a secondary skimmer basket right before the pump inlet, don’t forget to clean that one too. Mine is always clogged with skinny pine needles that made it past the primary baskets.
3. If both baskets are clean and the pressure is still low, check the pump impeller.  Sometimes I find pine needles in mine that I have to scoop out with my finger.

After taking these steps, check the pressure again to see if it has improved. Once it has, you’re ready to move on to the next steps.

Keep the pump running!

Also as we move on to the next steps, if you normally keep your pool pump on a timer, reset it to run all day long. This will help ensure that the green water gets through the filter as quickly as possible.

2- Clean out any organics you can see

If you can look into your green or cloudy pool water and see anything in there that shouldn’t be such as dead leaves, branches, etc., these are called “organics”, and they need to be scooped out of your pool immediately!

Why is that? Organics are what algae feed on inside of pools. Think of every dead leaf you see as the algae equivalent of a tasty meal!

So by removing the organics, you’ll eliminate algae’s main source of food, and this will help keep your pool water crystal-clear blue (after we’ve gone through the rest of these steps).

Start by skimming the top of your pool and removing anything that obviously should not be there. If you can see further into the water towards the bottom of your pool, try to scoop or vacuum what you can. If you’re unfortunate enough that your pool water looks like the Black Lagoon and you simply can’t see anything beyond the upper surface, then don’t worry. Later in Step 7 below, we’ll talk more about cleaning the bottom of the pool later as the water becomes more transparent, and give you some advice on pool vacuums.

3- Measure your chemical levels

Before we can add any pool chemicals, we need to first know what we’re working with.  To get started, take a test strip and measure your chemical levels.

In particular, we want to know the pH level of your water. Balancing your pH will affect the effectiveness of all the other chemicals.  So it will be helpful to make sure it’s as close to good as possible.

Compare your test strip results to the back of the package.

• If your pH is too low, add some pH plus (Sodium Carbonate).
• If it’s too high, add some pH minus (Sodium Bisulfate).

Amazon and pretty much every big box store (such as Walmart) has some version of these two products.

4- Raise the chlorine level

Once the pH is balanced, the next step is to zap all the algae in your pool water with some sanitizer. For most pools, this will mean adding chlorine into the circulation and increasing the levels as quickly as possible.

Depending on the design of your pool, there are lots of different ways to feed chlorine into pool

• Cartridges
• Tablets
• Powder
• Liquid
• Etc.

Our pool is a salt-water system that chlorinates using bags of pool salt and is generally not as harsh on your skin and eyes as traditional chlorine systems.

Liquid Chlorine

In addition to your normal method of chlorine delivery, I’ve always found the quickest way to ramp up the chlorine level in the pool is to dump in a few bottles of liquid chlorine. Again, it can be purchased for relatively cheap at any big-box store or pool supply retailer (I typically pay less than $20 for a case of 4).

Use approximately 2 gallons for every 10,000 gallons of water you have.  If your water is really nasty, feel free to be generous with another gallon or two. Wait a few hours for the chlorine to circulate and measure your chemical levels to make sure it’s increasing.

Side note: Speaking from experience, liquid chlorine does a really good job of destroying your clothes if it splashes back on you.  My advice is to either pour it into the pool as slowly and carefully as possible, or wear something you wouldn’t mind getting a discolored spot or two on.

5- Shock your pool to get rid of the green color

After getting the chlorine level of the pool water up, the next step is to increase its intensity by using something called “shock” (also known as calcium hypochlorite).

What does shock do? Shock is a chemical that temporarily raises the level of free chlorine in your pool to the point where algae and bacteria are destroyed.

Imagine the chlorine in your pool is a really strong person trying to fight crime. But when you add in shock, it temporarily turns that strong person into the Incredible Hulk. The bad stuff in your pool doesn’t stand a chance!

Adding shock to your pool is very simple. Go to the deep end and pour in about 2 one-pound bags for every 10,000 gallons of pool water you have.

Again, let the pump run continuously overnight. Within 24 hours as the shock does its job of killing algae and bacteria, you should start to notice the water cool change from green to blue. Don’t be alarmed if its a cloudy color; we’ll address that in the next step.

If your water is REALLY green …

If your water looks dark green or even almost black, then you’ve got a more advanced algae problem. This means you’re going to want to throw in a few extra bags of shock or repeat this step a few times.

6- How to get rid of the cloudy water

If your water is now a shade of blue but cloudy, don’t fear!  You’re on the right track and almost there.

The cloudiness you see is all the dead algae floating around. How do we get rid of it? You basically have two options:

Option 1 – Wait …

Run the pool pump for a really long time until all of the dead stuff naturally passes through the filter. However, keep in mind that this could take several days or even weeks to accomplish.

Option 2 (my preference) – Use some pool water clarifier

Clarifier is a chemical that combines with all the dead stuff in your pool and makes it heavier, causing it to sink to the bottom of your pool for easier clean up.

Personally, I’ve been using a product called Super Blue for years and it gets the job done quick.

Using it is very simple. Grab a 5-gallon bucket from the hardware and mix the clarifier in some water according to the directions on the product. Pour it into the perimeter of your pool and wait a few hours. Generally by the next day you’ll notice that the pool water is less cloudy and most of the dead particles are now on the bottom and walls of your pool.

7- Clean up the remaining scum

Now that you can finally see through your pool water, then last step is to clean, clean, clean!

By now all the dead algae should appear as brown specs along the bottom and walls of your pool. To clean this up, you’ll want to vacuum your pool and brush the walls.

Vacuuming your pool

Pool vacuums come in nearly every shape and size. Some are just hoses that connect to your pump return line while others are completely automatic. Depending on your budget, you can get as fancy as you want.

There are two that I like to use:

• I use this battery powered pool vacuum called the Pool Blaster. It simply connects to my skimmer pole and then I manually run it along the bottom of the floor sucking up organics and brown scum. I’ll admit – It takes a long time to clean and the battery doesn’t last more than an hour, but this little vacuum does get the job done!
• We also use an automatic pool vacuum called the Polaris. This is a rolling device that mates to your pump outlet and uses the water pressure to clean up the bottom of the pool. All day and all night, as long as your pump is running, this vacuum is rolling along the bottom of your pool and cleaning as it goes. Pretty effortless!

Brushing your pool walls

In addition to vacuuming the bottom of the pool, you’ll also want to take a pool brush and brush down the sides of your pool. This is to get algae off the walls and free-floating into the water where they can be sucked into the filtration system.

If you’ve got some dark spots on your pool walls or bottom surface that won’t seem to brush off, you might have some more stubborn algae. For this, you’ll need a brush with harder wire bristles instead of the normal soft nylon bristles.

8- Keep up on your maintenance

Once things are relatively back to normal and the water is looking clear blue, be sure not to stray from its weekly scheduled maintenance. Otherwise you’ll be right back at step one again!

In general, your maintenance should include the following:

• Balancing the pH
• Adding chlorine
• Shocking the water and other algae killing chemicals (like Pool Perfect Phos Free, etc)
• Vacuuming the walls and bottom of the pool
• Cleaning / back-washing the filter
• Etc.

Stay on top of this, and you’ll get plenty of great, relaxing days floating around in crystal-clear water.

Good luck and enjoy!

Featured image courtesy of Flickr / Sean Davis