Does Chlorine Raise Or Lower pH?


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Contrary to what some might think, chlorine raises the pH level of the water. When you mix chlorine with water, the pH level typically increases and becomes more alkaline/basic. Therefore, you must monitor and adjust the pH level accordingly when using chlorine as a disinfectant.

If you’re a pool owner or a curious individual with a thirst for knowledge, you’ve probably wondered about the relationship between chlorine and pH levels. 

In this article, we will explore the differences between chlorine and pH and how they interact. 

Does Chlorine Cause pH To Rise?

When maintaining a swimming pool, pH balance is of utmost importance. The pH level indicates whether the water is acidic or alkaline, and it needs to be within the correct range for the water to be safe and comfortable for swimmers. One common misconception is that chlorine causes the pH level to rise. 

First, you need to understand how chlorine works in a pool. Hypochlorite ions (OCl-) and hypochlorous acid (HOCl) form, when chlorine mixes with water and ion exchange occurs. These two compounds work together to kill bacteria and other microorganisms present in the water. However, neither of these compounds directly affects the pH level.

The pH level is determined by the concentration of hydrogen ions (H+) in the water. When an acid is added to water, it increases the concentration of hydrogen ions, resulting in a lower pH value. On the other hand, when an alkaline substance is added, it decreases the concentration of hydrogen ions, leading to a higher pH value. 

Chlorine itself is a neutral substance and does not have any effect on the pH level. However, the type of chlorine that is commonly used in pools, known as calcium hypochlorite, does have a slight alkaline effect. This means that when calcium hypochlorite dissolves in water, it releases hydroxide ions (OH-) which can raise the pH slightly.

So while chlorine itself may not cause the pH level to rise significantly, the type of chlorine used in pools can have a minor impact on the pH balance. So you need to be aware of this and regularly test and adjust the pH level accordingly.

What Causes pH To Rise In Pools?

One of the main culprits behind this issue is the total alkalinity of your pool water. Total alkalinity refers to the number of alkaline substances, such as bicarbonates and carbonates dissolved in the water. These substances act as buffers, helping to stabilize the pH level, however, if the total alkalinity is too high, it can cause the pH to rise. 

When the total alkalinity is high, it makes it difficult for the pH level to be adjusted and stabilized, so, even if you add acid to lower the pH, it may not have a significant effect. This is because the high total alkalinity counteracts the efforts to lower the pH, causing it to remain high or even increase.

To prevent this issue, it’s important to regularly test and adjust the total alkalinity of your pool water. Ideally, the total alkalinity should be kept within a range of 80-120 parts per million (ppm). By keeping the total alkalinity in check, you’ll have better control over the pH level of your pool water.

Ideal Levels Of Chlorine & pH

Centers for Disease Control and Prevention (CDC) advise swimming pools to have a pH of 7.2-7.8, as this range ensures optimal comfort for swimmers and prevents any potential damage to the pool equipment.

The ideal chlorine level for a swimming pool is at least 1 part per million (ppm), which effectively disinfects the water without causing any irritation to your swimmers’ eyes or skin. In hot tubs/spas, the chlorine concentration should be at least 3 ppm. 

pH Levels & Chlorine Effectiveness

As the pH increases (becomes more alkaline/basic), the effectiveness of chlorine is dramatically reduced. 

For example, when the pH level is 5.5, chlorine effectiveness is at 100%. However, at a pH of 7.5, the chlorine effectiveness drops to 45%, and when the pH increases to 8.0, it continues to drop to 25% effectiveness. 

Liquid Chlorine Vs Chlorine Tablets To Raise The pH 

Liquid chlorine is a popular choice for many pool owners when raising the pH level because it is a fast-acting and effective option. Liquid chlorine can disperse quickly in the water, plus you have more control over the amount you add, allowing you to adjust the pH level precisely. It is also a versatile option for both regular maintenance and shock treatments.

On the other hand, chlorine tablets are another option for raising the pH level. These tablets are slow-dissolving and can provide a steady release of chlorine into the water over a longer period. This can be beneficial if you have a busy schedule and want to minimize the frequency of adding chlorine. However, it is important to note that chlorine tablets do not dissolve as quickly as liquid chlorine, so it may take longer to see results.

Ultimately, the choice between liquid chlorine and chlorine tablets depends on your specific needs and preferences.

Does pH Lower If The Chlorine Is High?

If chlorine is added in excessive amounts, it can result in an imbalance of the pool’s chemistry. This imbalance can cause the pH level to drift towards the acidic side. However, it’s important to note that this is not a direct cause-and-effect relationship. Factors such as sunlight, rainwater, temperature, and the presence of other chemicals can also affect the pH level.

Is Too Much Chlorine Dangerous For Pools?

While chlorine is effective at killing harmful bacteria and viruses, in high concentrations it can have negative effects on the health of bathers and swimmers.

One of the main concerns with excessive chlorine in pools is the potential for respiratory problems. When chlorine combines with organic matter like sweat, urine, and skin cells, it forms chemical compounds called chloramines. These chloramines can be released into the air above the pool and inhaled by swimmers, leading to respiratory irritation that can cause symptoms such as coughing, wheezing, and shortness of breath, particularly in individuals with asthma or other respiratory conditions.

Another issue with too much chlorine in pools is the impact on the skin and eyes. Chlorine is a harsh chemical that can strip the natural oils from the skin, leaving it dry and irritated. It can also cause redness and itching, particularly in individuals with sensitive skin or conditions such as eczema or dermatitis. In addition, chlorine can irritate the eyes and lead to redness, burning, and blurred vision. This is why it is highly advised for bathers and swimmers to rinse off thoroughly after swimming in chlorinated pools and use moisturizing creams and eye drops to alleviate any discomfort.

Excessive chlorine can also have negative effects on the environment. When chlorine-treated water is discharged into rivers or oceans, it can harm aquatic life by disrupting the natural balance of chemicals in the water. In turn, this can cause the death of fish and other organisms that rely on these ecosystems for survival. Therefore, it is crucial for you to carefully monitor and regulate the amount of chlorine used in your pool to reduce the impact on both human health and the environment.

How To Measure Chlorine Levels In Water?

One of the most simple and common ways to measure chlorine levels in water is by using a test kit. These kits usually contain test strips that change color in the presence of chlorine. Simply dip the strip into the water for a few seconds, and then compare the color change to the provided chart. Color test strips give you an estimate of the chlorine concentration in your water.

Another method involves using a portable chlorine meter. These devices are more accurate than test kits and work by measuring the electrical conductivity of the water, which is directly related to the chlorine concentration. Chlorine meters offer real-time readings and more precise and reliable measurements over basic test kits. 

Regardless of the type of measuring device you choose, the most essential factor is to monitor the chlorine levels regularly. 

How To Measure The pH Of Water?

The two main methods to measure pH: using a pH meter or a pH test kit.

A pH meter is a device specifically designed to measure the acidity or alkalinity of a solution. The pH probe is inserted into the water sample and connected to a digital display. The probe measures the electrical potential difference between itself and a reference electrode, which is converted into a pH reading. This method provides accurate and precise results, making it ideal for scientific or professional use. However, pH meters can be fairly expensive and require regular calibration and maintenance.

On the other hand, a pH test kit offers a more affordable and convenient option for measuring the pH of water. These kits typically include test strips or liquid reagents that change color based on the pH level of the water. The approximate pH value is determined by comparing the color change on the provided color chart. While pH test kits are not as accurate as a pH meter, test kits are suitable for general purposes and home use. They are also portable and user-friendly, making them accessible to anyone.

Should I Raise The Chlorine Or Lower The pH First?

The answer to this question depends on the severity of the imbalance, but generally, it is recommended to address the pH level first. Maintaining the proper pH range of 7.2-7.8 is crucial for the effectiveness of chlorine. If the pH is too high, chlorine becomes less effective, and if it’s too low, as previously mentioned, it can irritate swimmers’ skin. Once the pH is within the desired range, you can focus on raising or lowering the chlorine level as needed.

Alternative Methods To Raising The pH Of The Water

In addition to using a pH increaser like chlorine, there are some alternative ways to increase the pH of your swimming pool/hot tub/spa water.

Baking soda, also known as sodium bicarbonate, is a household item that you likely already have in your kitchen, if not, you can easily find it in your local grocery store. Baking soda acts as a natural buffer and can help stabilize the pH level of the water. To use baking soda, you can simply sprinkle it directly into the pool while the pump is running. Just like dosing your water with chlorine, it is important to add baking soda in small amounts and retest the water after each addition to prevent drastic changes in pH.

If you don’t want to add any chemicals, you may want to consider using aeration or air injection to raise the pH of your pool water. Aeration involves increasing the exposure of the water to air, which helps to release carbon dioxide and raise the pH level by installing a fountain or waterfall feature in your pool, or by using an air pump or air stone. Air injection, on the other hand, involves injecting air directly into the water using specialized equipment. 


Having a swimming pool is a wonderful luxury, but it also comes with the responsibility of maintaining the water quality. One important aspect of this maintenance is ensuring that the pH level and chlorine of the pool water are balanced and understanding the relationship between the two.

If you have any questions regarding the pH level or would like to know more about testing the water chemistry inside of your swimming pool or hot tub, do not hesitate to contact the world-class team at Atlas Scientific

pH Probes & Sensors

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