Introduction:
As pool owners, we all want to enjoy sparkling, inviting waters that are safe for swimming. However, achieving and maintaining that pristine pool condition requires more than just skimming leaves and adding chlorine. One crucial factor that often gets overlooked is the pH level of the pool water.
At Together Energy, we help you save 25-40% on the cost by optimising the way you manage your pool.
In this blog post, we'll help you understand the impact of pH on chlorine in your pool water and why keeping it within the optimal range is key to a healthy swimming environment. You want to ensure your chlorinator works effectively, giving you the best bang for your buck.
Understanding pH and its Impact on Pool Health:
pH is a measure of how acidic or alkaline a substance is, with values ranging from 0 to 14. In the context of pool water, the ideal pH range for pool water is between 7.2 and 7.8. When the pH strays outside of this range, it can have significant implications for pool health and for your electricity bill.
The Role of pH in Chlorine Effectiveness:
One of the primary reasons why maintaining the right pH level is crucial for pool maintenance is its impact on the effectiveness of chlorine.
Whether you use a chlorinator, liquid, granular chlorine or tablets, eventually chlorine exists in two forms in water: hypochlorous acid (HOCl) and hypochlorite ion (OCl-).
Both work as disinfectants to kill bacteria and other harmful microorganisms in your pool through oxidative reactions. However, it turns out that hypochlorous acid is a much stronger sanitizer than hypochlorite ion. We're not talking about a small difference either, HOCL is 80 times more effective at neutralising bacteria than OCl-.
Now here's the key take-away from this post: the pH level of the pool water is what determines how much of each form of chlorine is present in the water, as shown in Figure 1 below.
When the pH level of the pool water is within the optimal range of 7.2 to 7.6, the majority of the chlorine still exists in the form of hypochlorous acid. This means that the pool water is more efficient at dealing with bacteria and algae, resulting in a cleaner and clearer pool.
However, when the pH rises above 7.5, the balance shifts, quickly, and the effectiveness of the chlorine is compromised. Your chlorinator ends up producing chlorine that simply doesn't work.
pH tends to increase over time:
In saltwater pools, the chlorinator generates chlorine by electrolyzing salt dissolved in the water. During this process, chlorine gas (Cl2) is produced along with hydrogen gas (H2) at the anode, and hydroxide ions (OH-) are produced at the cathode. The production of hydroxide ions from the cathode reaction increases the pH of the pool water.
The chlorine gas dissolves in the water and reacts with water to form hypochlorous acid (HOCl), the most active sanitizer in the pool, and hypochlorite ions (OCl-), which is 80x less effective.
Additionally, the process of aeration, which occurs as water passes through the chlorinator cell, can lead to the escape of carbon dioxide (CO2) from the pool water. That's the bubbles you see escaping from the pool return nozzles. Carbon dioxide is an acidic compound that helps buffer the pH of the water. When it escapes, the pH tends to rise, contributing to the overall increase in pH levels.
Therefore, the combined effect of hydroxide ion production and CO2 loss can cause the pH of saltwater pool water to drift upwards over time. It's just a fact that if you have a salt water pool with a chlorinator, the pH will tend to drift up over time.
This highlights the importance of regularly monitoring and adjusting the pH to maintain the optimal balance for a clean and clear pool.
Consequences of Imbalanced pH:
Obviously you don't want to go the other way either. If the pH level of the pool water is too low (acidic), it can lead to corrosion of pool equipment, irritation of skin and eyes, and inefficiency of chlorine. On the other hand, if the pH is too high (alkaline), it can result in scale formation, cloudy water, and reduced effectiveness of chlorine. In either case, maintaining an imbalanced pH can result in increased maintenance costs and discomfort for swimmers.
Tips for Maintaining pH Balance:
Regularly test the pH level of your pool water using a reliable test kit. These days most of us either take a water sample to the pool shop or use the test strips.
Adjust the pH as needed using pH increaser (sodium carbonate) or pH decreaser (pool acid).
Monitor other factors that can influence pH, such as rainfall, bather load, and the use of pool chemicals.
Ensure your alkalinity and calcium hardness are also where they should be. We'll write another post on this soon.
Most importantly, do it regularly otherwise the pH may creep up on you.
Conclusion:
Maintaining the right pH level is essential for ensuring a clean, clear, and safe swimming pool. By keeping the pH within the optimal range of 7.2 to 7.8, pool owners can maximize the effectiveness of chlorine and minimize maintenance issues. Best of all, if you're optimising the use of your chlorinator, you can run it less time and for more years, saving you money and the environment.
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