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How To Lower Alkalinity In A Pool

To lower the alkalinity of your pool, the most effective way is to introduce either muriatic acid or dry acid (sodium bisulfate) into your swimming pool. Knowing the causes of high alkalinity in your pool is essential to prevent it. 

Your pool can last from 10 to 30 years, depending on the material used to make it. During this period, your pool’s alkalinity should stay between 80 and 120 parts per million. If it gets higher than this value, it can negatively affect you and your pool’s framework. It is, therefore, important to control this value within the recommended range.

In this article, I will provide some insights on how to measure and lower your pool’s alkalinity using some of the most commonly employed methods. At the end of the article, I will answer some frequently asked questions about lowering your pool alkalinity. 

How To Lower Alkalinity In A Pool

What Is The Alkalinity Of The Pool?

The alkalinity of your pool is the capacity of the water inside the pool to resist acidification. This is the measure of the ability of your swimming pool to prevent changes in pH when acids or bases are added to it. 

Ideally, the alkalinity of your pool should be between 80 and 120 parts per million. When this alkalinity value gets too high, it can have several consequences, such as negatively affecting chlorine’s ability to function effectively and irritation of eyes and skin. 

What Causes High Alkalinity In A Pool?

Now you might be wondering, what is the cause of high alkalinity in the pool? The following are some important causes of your swimming pool being too alkaline. 

  • Substances in the pool, such as sunblock, creams, oils, alcohol, and other alkaline chemicals, can cause high alkalinity. 
  • Shocking the pool can also increase its alkalinity. Chlorine-based pool shocks are highly alkaline and will raise pH and, therefore, alkalinity.
  • Hose water is often alkaline and may raise the alkalinity of the pool. Anything you add to a swimming pool will affect the water’s chemistry. Check the pool’s alkalinity before and after adding rainwater or hose water. Most people must add several inches of water to their swimming pool each week if it’s uncovered.
  • Algal blooms, plants, and animals can also cause changes in your pool’s alkalinity. Specifically, algae are usually high in pH, so they might cause high alkalinity in the pool. 
  • Rapid temperature changes may also affect the alkalinity. Many pool owners add acid at the beginning of spring and summer. Always test the pool before adding chemicals. The last thing you need is to battle adjusting the pool’s chemicals constantly.
  • If your pool is made of plaster, there is a chance that the alkalinity of your pool is high. Plaster consists of calcium, which can result in a high pH, thus leading to higher alkalinity.
  • Using saltwater in the pool could raise its alkalinity.  

Testing The Alkalinity Of Your Pool

There are several ways to check the alkalinity of your pool.

The most commonly used ones include:

  • Using test strips like the JNW Pool and Spa Test Strips tells you what you must adjust your pool’s chemistry. Just simply dip the test strip into the water for about 30 seconds. Then remove the strip from the water and compare it with the chart on the container to get an idea of your pool’s alkalinity. It is a relatively quick and cheap way of getting an idea of your pool’s alkalinity.
  • Another way of determining the alkalinity of your pool is to use a chemical set. Multiple drops of Poolmaster Essential Chemistry Set can help you monitor your pool’s condition. It is more accurate than test strips. However, it is more time-consuming, and obtaining the result might be difficult.
  • You can also use digital testers to accurately read your pool’s alkalinity. Try the AquaChek TruTest Digital Reader for quick results. You’ll be able to see the alkalinity, pH, chlorine, and a few other details. These tend to be accurate and do not lose effectiveness over time, but they are slightly more expensive than other options. 

Risks Of High Alkalinity In A Pool

You might be wondering what the consequences of high alkalinity in the pool would be. Some of the risks related to high pool alkalinity include the following:

  • High pH: This could lead to skin rashes, cloudy water, and a reduction in the effectiveness of chlorine.
  • Scaling on the walls: This is due to the formation of calcium carbonate that solidifies on the pool walls. Its presence causes high pH, which will have the effects described above. 
  • Metal components may get damaged: Leading to the presence of metal in the pool water. This metal may stain the pool water or alter the pool’s pH. 
  • Water gets cloudy: Which indicates an imbalance in the pH of the water. This may harm the pool filter or promote the growth of harmful bacteria and algae within the pool. 
  • Irritation: Skin, eyes, hair, and other body parts feel irritable.
  • The effectiveness of chlorine is reduced: A rise in pH reduces chlorine’s ability to clear the water from harmful bacteria and other microorganisms. These microorganisms might cause local or systemic infections in your body. 
  • Filters may get clogged: Cloudy water may clog filters. This may result in reduced water flow, inadequate water filtration, and an increased chance of algal blooms. 
  • High calcium levels: An increased amount of calcium may form calcium carbonate, which not only causes scaling on the walls of the pool but also causes an increase in pH and alkalinity. 

How To Reduce Alkalinity In A Pool?

Now that we’ve discussed the basics of alkalinity, let’s answer the question relating to how to lower the alkalinity in a pool. The following are some ways that you can use to solve the problem of high pool alkalinity:

Add Muriatic Acid (Hydrochloric Acid)

The best way to lower the alkalinity of your pool is to add acid. Two types of such acids have been commonly used to reduce the alkalinity of pools. The first one is muriatic acid. This acid comes in liquid form and is very effective in lowering the alkalinity of your pool. 

Muriatic acid works quicker than any other acid in the pool industry. That said, it needs to be thoroughly circulated, or it’ll stain and damage the swimming pool. It’s also much more corrosive, so you must pay close attention when adding it to the water. The Champion AcidBlue Muriatic Acid is excellent for quick effectiveness, easy dosage, and acid washes.

Add Sodium Bisulfate (Dry Acid)

The second acid used to reduce the alkalinity of your pool is dry acid, also known as sodium bisulfate. This is ideal for a vinyl or fiberglass swimming pool since it is less harsh than muriatic acid. 

As the name suggests, sodium bisulfate is available in powder form; therefore, it must be added to water in a separate container before adding it to your pool. It is, however, cheaper than muriatic acid. If you prefer dry acid, try EcoClean pH Down

Use Pool Covers

Pool covers can prevent changes in your pool’s chemistry by limiting evaporation, chlorine loss, or adding debris into your pool. This can lead to your pool maintaining its alkalinity. 

  • Solar covers prevent debris from getting into the water. All debris has varying pH levels that influence your pool’s alkalinity. If too many algae, leaves, pet hair, and other organic matter are in the water, you’ll have difficulty maintaining the pH and alkalinity. Use a solar cover to keep the debris out of the pool throughout the week.
  • You can use a pool blanket to prevent your alkaline chemicals from evaporating. Pool covers keep the chemicals and water in the pool. If you have a cover, you won’t have to add acid or soda ash to adjust the pH and alkalinity nearly as often. Furthermore, the alkalinity will promote chlorine effectiveness.

Use Lemon Juice

Lemon juice is acidic and is suitable as an alternative to the acids mentioned above. However, you must limit its use and should only use it when other options aren’t available. This is because, when used excessively, lemon juice can cause acidic corrosion and increased phosphates.

This increase in phosphate levels may allow algal growth, which can further affect the alkalinity of your pool. It is, therefore, essential to check the phosphate levels of your pool when using lemon juice. 

Add Rainwater

Rainwater may also be used as an alternative option to increase the alkalinity of your pool when other options aren’t available. Rainwater is often acidic, and adding it to your pool can reduce its alkalinity. 

You should consider leaving your pool open when it’s raining or collecting rainwater in collection barrels to add to your pool later. Remember to check the phosphate levels of your pool after adding rainwater and correct any excess phosphates to limit algae growth. 

How to Calculate The Amount of Acid My Pool Needs?

Now, you might wonder, how much acid you need to put in my pool to lower its alkalinity? To find this amount, you need to consider the following measurements:

  • Pool volume 
  • Current pH 
  • Present alkalinity 
  • Desired alkalinity (between 80 and 120 ppm)
  • The acid you will be using (sodium bisulfate or muriatic acid)
  • The percentage of acid in the product that you are using

After determining these values, you can put them in the Pool Acid Dose Calculator and obtain the amount of acid your pool needs. 

Precautions

There are several points you should keep in mind while adding acid to your pool:

  • Check the alkalinity of your pool before adding acid.
  • Always wear protective clothing such as gloves, coats, and goggles to prevent yourself and your clothes from getting damaged by the acid.
  • Consider diluting your acid if your acid is of a high concentration (above 50%)
  • You should add acid by walking around the pool rather than dumping it all in the same spot.
  • Avoid adding the acid too close to the edge or near metallic objects.
  • Use the pump for about an hour after adding the acid so that the acid gets mixed evenly throughout the pool.
  • Check the alkalinity of your pool a day after adding acid.

Conclusion 

You can lower the alkalinity of your pool by using substances such as muriatic acid and dry acid and alternatives such as lemon juice and rainwater. It is vital to eliminate the cause of the alkalinity by regularly checking your pool’s alkalinity through the methods I mentioned in this article. Maintaining alkalinity between 80 and 120 ppm can prevent damage to your pool and other adverse effects on those who use it. 

FAQs

Will shocking the pool lower alkalinity?

Shocking your pool will not lower its alkalinity. Since chlorine-based shocks are alkaline, doing so will increase your pool’s pH. The increase in pH will cause an increase in alkalinity. 

Will alkalinity decrease on its own?

The alkalinity will decrease if you leave the pool cover off during a rainstorm. However, rainwater can add phosphates and nitrates to the water.

They’ll bring algae blooms, which could increase the pH and alkalinity in the long run. It’s best to manually adjust the alkalinity to prevent it from harming the pool’s chemistry.

Does baking soda lower alkalinity in a pool?

No, baking soda will not lower the alkalinity of your pool. Instead, it will increase the pH and, thus, the alkalinity. This is because baking soda is composed of sodium bicarbonate which is alkaline in nature.

To lower the alkalinity of your pool, you should use acids such as muriatic acid and dry acid. If your goal is to increase the alkalinity of your pool, then you can use baking soda.

How To Lower Alkalinity Without Lowering Ph?

If you’re looking to lower the alkalinity of your pool without lowering the pH, then it can be done in two steps. In the first step, you will use acid to reduce the alkalinity.

This will, however, also result in a drop in pH. To counter that, in the second step, you will raise the pH by aerating the pool. This way, your pH will return to normal while the alkalinity will be lowered. 

Author

  • Jonah Ryan

    Jonah has worked for several years in the swimming pool industry installing and repairing equipment, treating pools with chemicals, and fixing damaged liners. He also has plumbing and electrical experience with air conditioning, ceiling fans, boilers, and more. When he's not writing for Temperature Master, he's usually writing for his own websites, LawnCareLessons.com and DIYByHand.com.

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