How To Make My Pool Water Blue

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Don’t you just hate it when you open your pool every spring and are met by the murky, swampish, green waters? Though expected, it still comes as a shock to many. This shock can soon turn into desperation for most new pool owners after trying everything their pool supply store recommends, but nothing seems to work.

To turn the green pool into the therapeutic crystal blue waters that you long for, you only need to follow a few simple steps, as we outline below.

But first, you need to understand why you have a green pool in the first place.

What Causes A Green Pool

In addition to being slimy and disgusting, the green water is dangerous to swim in as you don’t know the kind of microorganisms flourishing in it. We recommend avoiding the cloudy green waters as they could lead to infections.

1. Algae

The culprit responsible for the green water is algae. Algae thrive in stagnant, unbalanced waters. And a poorly covered pool with the pool pump turned off becomes a breeding ground for the stuff. Organic debris on the pool surface or inside the pool also contributes immensely to the multiplication of algae as it feeds on them.

2. Out Of Balance Water

Pool water balance depends on five factors: alkalinity, pH, calcium hardness, stabilizers, and total dissolved solids. Chlorine, the most common sanitizer used for swimming pools, does not work efficiently out of balance water. As a result, algae and other organisms thrive in the pool leading to green water.

Stabilizers are essential in ensuring optimum chlorine levels are maintained to prevent the sun UV rays from depleting them.

3. Faulty Pool Filter

It can lead to murky water entering the pool either during refilling or topping up the pool waters. This water increases the organic content of the pool, which contributes to algae growth. A faulty pool filter can also lead to poor water circulation and further enables algae to attach to the pool finish.

4. Weather Conditions

During the hot months, the evaporation rate of the pool water is high, leading to increased topping up. With every freshwater added, the chlorine level becomes diluted, lowering its efficiency to kill algae. Wind also deposits organic and inorganic matter into the pool, the same as rain which washes it into the swimming pool. The presence of debris in the pool water may lead to an algae bloom.

How To Make The Green Water Blue Again

The reason pool water looks blue is because water does not absorb it from the light spectrum. Thus if there is the presence of matter absorbing the blue hue, it loses its blue color. Getting rid of all that matter turns the water blue again.

1. Get The Pump Working

The first step to getting rid of all the algae giving you a green pool is running the pump. The primary purpose of the pool pump is to circulate the water and ensure it passes through the pool filter. All the debris that has collected over winter is filtered out into the skimmer basket. Ensure that your pump is working correctly by;

  • Manually checking whether the pressure at the jets is strong enough. You can simply do this by placing your hand in the pool in front of a jet. If you can’t feel anything or the water pressure on your hand is weak, a system check is required.
  • Sometimes you will find a pressure gauge on the filter or pump. If it’s reading zero or near zero, it means you need to check your system.

No pressure or zero reading indicates a clogged water circulation system. You can quickly correct this by emptying the skimmer basket. Depending on the type of pump, it may have a secondary skimmer basket that filters anything that escapes the primary skimmer basket. Empty this one too. If there is still no change in the water pressure, a check on the impeller may reveal some tiny debris like pine needles which you can scoop out using your fingers.

It is essential to ensure the pump is running before taking any other measures because it is pointless if there is no water circulation. Also, keep the pump running all day to filter the debris faster.

2. Clean Out Any Organics From The Swimming Pool

Organics refer to all the dead matter, such as dead leaves and branches you find floating on the pool surface or inside the pool. They form an excellent food source for the algae. If you do not eliminate the primary food source, more algae will return, making the exercise of turning the pool water blue futile.

Doing this is very simple. You must remove anything visible on the pool surface. The bottom of the pool depends on how opaque the water is. If your situation is not bad enough and you can see the bottom of the pool, vacuum the debris or scoop it out. But, if you can’t see anything beyond the pool surface, don’t despair, as you will clean the organics several steps later when the water is a bit clearer.

3. Measure The Level Of The Chemicals Of Your Swimming Pool

The pool water chemical balance is vital for the blue color of the pool and the safety of the swimmers. For instance, if the pH is extreme, it will affect the skin and how chlorine works. You will need to take several parameters such as pH, calcium hardness, free chlorine, total chlorine, alkalinity, and cyanuric acid.

The measurements can be taken using readily available kits that one may purchase online. They came with instructions on using and the measures you will need to take depending on your result. If the pH is too high, you will add pH minus(sodium bisulfate or a version of it), but a pH plus is required if it is too low. Sodium carbonate or a chemical version of it is used. Getting the pH of your pool water to optimal levels is essential as it affects how all the other chemicals work.

Balance Calcium hardness and cyanuric acid by draining the pool and adding fresh water depending on the levels. If you carry out this step, ensure you brush the walls to remove the dead algae before introducing the freshwater. You can also check the filter after draining to ensure calcium deposits do not block it.

Finally, depending on the free chlorine levels and total chlorine, you will need to add more to balance them. Chlorine can be added through the usual means of cartridge, tablets, powder, or liquid, depending on your pool type. Though the other methods are effective, adding liquid chlorine is more straightforward and does not need any preparation. Dump a few bottles into the pool depending on the volume of your pool and the test results. Remember to keep it away from your clothes.

Measure the chemical levels again to ensure they are at optimum levels.

Killing The Algae

Chlorine is used to kill algae and other microbes in the swimming pool. But due to the high level of algae in your pool right now, you will need to apply shock treatment. Shock simply means adding a temporary boost of chlorine to the normal levels to ensure all the algae is dead. In every 10,000 gallons of water, add a bag of shock treatment and pour it at the deep end. Leave it overnight and keep the pump running throughout.

If your water is dark green to almost black, you can either repeat the process or add another bag for every 10,000 gallons of water. Within 24hrs there should be a change in the watercolor. If you notice the water is changing from green to blue, but it’s still cloudy, that should not worry you.

Removing The Dead Algae

The dead algae floating in the pool water is responsible for the cloudy look in your swimming pool at this moment. There are two ways to remove it.

1. Leave The Pump Running

If you leave the pump running, it may take you several days or weeks before you turn the water from cloudy to crystal clear blue. Though it takes time, eventually, all the dead algae pass through the filter and are removed. But you want to enjoy your pool now that you can see blue water.

2. Use A Clarifier

It is a solution that combines with all the dead algae and makes them heavy to sink to the bottom of the pool. Once you get your clarifier, mix it with water in a 5-gallon bucket, following the instructions. Pour it on the perimeter of the swimming pool and wait overnight. The next day, the pool should be clear with all the dead algae at the bottom or on the swimming pool wall.

3. Vacuuming The Pool

Cleaning the pool at this point is easy because you can see through the clear blue water. A vacuum can be as simple as a hose connected to the pump’s return line, or it may be automatic. Whatever the case, vacuums make the work of cleaning dead algae from the bottom of the pool easy. Ensure you thoroughly remove all the dead stuff.

4. Brushing The Walls Of The Pool

Vacuuming is just one step in ridding your pool of the dead algae, and you’ll need to take a pool brush and work on removing the algae attached to the walls. Sometimes you may need to use a stiff wire brush to remove the stubborn algae that won’t come off with the soft nylon bristles.

Ensure The Algae Does Not Come Back

After removing all the dead algae, it is essential to ensure it doesn’t come back. We do this by adding chlorinating tablets every week. The sun-protected chlorinating tablets are best for use during the day. Place them in the skimmer basket or a floater. Since you will be doing this regularly, it is advisable to buy the tablets in bulk. It is cheaper that way.

Another step is applying algaecide to the pool water. The first application should be 24hrs after applying shock treatment. The amount of algaecide you use depends on the volume of your pool. Subsequently, apply it every week before any signs of algae can be seen.

Maintain Swimmers Comfort

All the algae are gone, and you have taken measures to ensure it does not come back; you can now take a dip in the pool. No. Before you do, it is prudent to measure the chemical balance to be on the safe side. Take your kit and carry out the tests as per the instructions. Maintaining the right balance is crucial for the swimmer’s comfort and safety. Once you have the results, apply the balancers accordingly.

Some tests need you to download an app, while others need you to send the results for analysis before being advised in real-time. Choose the kit wisely, as the results will guide you on the balancers your pool needs. Once you apply the correct balancers, you can take out the floaters and enjoy your pool.


To maintain a healthy pool, you need to carry out some maintenance checks regularly. They ensure you have a blue pool throughout. Some of the weekly checks include;

  • Test the chemical balance of your pool every week
  • Apply balancers according to the results of your test
  • Rechlorinate your pool every week by applying a tablet
  • Shocking the water and applying algaecide
  • Vacuuming and brushing the bottom and walls of the pool
  • Ensuring the filter is clean by emptying the skimmer basket and backwashing the filter

Dedicating a day to cleaning your pool is the best way to ensure you never miss. You can opt for doing it every Friday as you anticipate the weekend. But during extreme weather conditions, you may need to do it twice every week. Whichever day you choose, don’t slack, and you will enjoy the refreshing blue water of your pool for a long time.

Problems You May Face

Sometimes even after carrying out all the necessary steps, you may still end up with a cloudy pool. Some of the reasons for this include;

  • The quality of chemicals used may be lacking, thus not doing a proper job
  • Sometimes rainwater makes the pool cloudy. You can prevent this type of cloudiness by covering the pool.

When buying chemicals for use on your pool, get high-quality chemicals from respectable suppliers.

Take Away

Over the colder months, the probability of your pool water turning green despite being covered is very high. Even if you are tempted, do not empty your pool thinking that when you refill it, you will have a blue pool. The science behind it does not work that way. Your pool water requires thorough cleaning and proper treatment to turn into the refreshing blue pool you love.

You are now armed with the knowledge to turn your pool blue at a lower cost than you would get from a pool cleaning service. Once you clean your pool, make sure you follow the weekly cleaning routine to keep it clean. It’s now time to enjoy your blue water pool. You deserve it.

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