The Ultimate Guide to Pool pH - Everything You Need To Know
Your pool’s pH is one of the most important factors of your overall water chemistry. Because pH levels play a large part in the effectiveness of other pool products, testing and regulating these levels is essential for maintaining any pool.
In this ultimate guide to pool pH, we will discuss what pH means and what ideal pH levels are in pools.
We also discuss the differences between total alkalinity and pH, how and when to test the pH of your pool, the effects of imbalanced pH, and how you can adjust your pool’s pH when needed.
What Is pH?
The term pH refers to the overall acidity of a substance. The pH scale ranges from 0-14, with 0 being highly acidic and 14 being highly alkaline. At the middle of the pH scale, at 7, substances are considered neutral.
Water itself is considered neutral. Pure, distilled water should ideally read at 7.0, but once exposed to the environment, many factors can influence the pH of water.
Ideal pH Levels in Pools
The ideal levels for swimming pool pH fall between 7.2-7.6. This range is slightly raised above the neutral point on the pH scale because levels that drop below 7.0 can have negative effects on your pool and swimmers.
Although pools with a pH reading of 7.0 are not necessarily harsh to the skin, a pH level of 7.4 is best for pools because this level is noted to be the most comfortable pH in terms of exposure to the eyes. For this reason, most eye drop products also have a pH of 7.4.
Total Alkalinity vs pH
Total alkalinity refers to the total amount of dissolved particles in water that contain alkaline properties. In a pool, ideal total alkalinity levels range from 80-120 parts per million (ppm).
When total alkalinity is present in your water, these constituents in your water work as a buffer to guard against rapid changes in pH.
Pools with less than adequate levels of total alkalinity are more likely to experience rapid changes in pH, especially when chemicals with acidic properties are introduced to the water. Maintaining ideal total alkalinity levels can also prevent water from becoming corrosively acidic, therefore guarding your pool’s equipment against deterioration.
How (And When) To Test Your Pool’s pH
To test your pool’s pH, you will need an appropriate test kit. Test kits are available as liquid solution kits, dip-method testing strips, and electronic pH meters. Most pool owners prefer to purchase a multi-test kit, as all kits typically include tests for pH.
Your pool’s pH levels, along with other crucial chemical levels such as free chlorine, should be measured 2-3 times per week. If you are using your pool frequently or otherwise have a large number of swimmers, it is recommended that you aim for 3 times per week.
You may also need to test your pool’s pH on other occasions, such as when you are balancing your pH or total alkalinity levels, and before or after the use of other specialised pool treatments.
Side Effects of Low pH Levels
Pool water with a low pH begins to develop acidic properties and become corrosive. This corrosive water has detrimental effects for your pool’s equipment and can also cause discomfort for swimmers in the form of eye and skin irritation.
One study has even found that extremely low pool pH can erode dental enamel!
If low pH water is left untreated, it will cause serious damage on your pool’s lining and equipment due to the corrosive properties of the water. This will start to develop as etching on surfaces, and can make any plastic elements of your pool turn brittle.
Surfaces surrounding your pool, such as concrete pathways or wooden decking that frequently come in contact with the pool water, are also susceptible to the damages of corrosive water.
Side Effects of High pH Levels
High pH can also cause many different problems in your pool. Most notably, high pH levels tend to lower the effectiveness of chlorine, especially if it is an indoor pool or if there is insufficient cyanuric acid.
This chlorine ineffectiveness can then allow microorganisms to reproduce within your water, leading to unsanitary conditions.
High pH in a pool is also known to cause cloudy water. This condition is sometimes a result of the chlorine ineffectiveness, and therefore indicates a large amount of bacterial activity in the water.
Cloudy pool water from high pH can also be caused by having too many dissolved solids in your water, such as calcium and other minerals.
Having cloudy water in your pool that is caused by high calcium hardness is typically a sign that calcium scale is beginning to develop. When your pool’s water contains too many dissolved solids, certain minerals and metals begin to fall out of the solution and form stains.
While low pH tends to induce burning sensations, water with a high pH tends to cause skin itchiness, and can include a temporary skin rash. High pH water should not come in contact with the eyes, nose, or other mucus membranes as this can cause intense irritation.
How To Adjust Your pH Levels
Before adjusting your pool’s pH levels, it is important to know the total alkalinity content of your pool.
Some products affect both of these properties, and these levels are also dependent on each other, so it is essential to know if your total alkalinity falls within the ideal range before making adjustments to your pool's pH.
If Your pH Is Too Low
If the pH in your pool is too low and needs to be increased, you can choose to use either sodium bicarbonate or soda ash to increase it. To decide which of these products is best for your situation, refer to the total alkalinity content of your pool.
Pools that have very low pH combined with low levels of total alkalinity benefit from using soda ash. This product works to increase both your total alkalinity and pH levels. Simply dissolve it in a bucket of pool water, then add it to the pool.
If your pool pH is only slightly too low and your alkalinity is also low, sodium bicarbonate (aka baking soda) is the better choice.
If your alkalinity is a bit high but your pH is too low, you may want to look at aerating your water. Aeration will drive off some of the CO₂ in your water, increasing your pH while slightly lowering the alkalinity.
Water features (like fountains and waterfalls) can achieve this, or you can buy dedicated aeration devices for your pool.
If Your pH Is Too High
If your pH is too high, you can choose to use either hydrochloric acid or sodium bisulphate to lower it. Both of these pH decreasing products also cause your pool’s total alkalinity levels to drop.
Deciding which one works best in your situation may depend on ease of use. Hydrochloric acid, sometimes called muriatic acid, is extremely effective at lowering pH, but it is dangerous to handle and to store. If you are not confident handling hazardous chemicals, or have children or pets in your home, it may be safer to choose sodium bisulphate.
Sodium bisulphate, also known as dry acid, is composed of a granulated formula that creates drops in your pool’s pH. Although this product should be handled with care, it has much less detrimental effects than hydrochloric acid in case of accidental exposure to the skin.
Your pool’s pH levels play a crucial role in maintaining the overall health of your pool’s water. Because of this, it is important to learn how to test and adjust your levels as needed so that you can avoid the detrimental effects of imbalanced pH.
Do you have any questions about swimming pool pH? Reach out to us in the comment section, we’d love to help!
A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.