Although talking about chemistry may cause your eyes to shut, you need to understand the basics of pH if you’re a pool owner and what that means for alkalinity of your pool water. pH is a scale that indicates how acidic or basic (alkaline) water is, based on the concentration of hydrogen ions. Pool alkalinity levels play a crucial role in your overall pool chemistry and keeping your swimming pool clean. So, below I cover everything you should know about total alkalinity, how to read it, and how to affect it. Let’s dive in.
What is Pool Alkalinity?
Pool alkalinity is the ability of water to resist acidification. Said another way, it denotes how cushioned the water is against sudden pH changes. Maintaining total alkalinity and pH is crucial for keeping your pool safe for swimmers.
The pH scale ranges from zero to 14, where seven is neutral. As most pool owners know, maintaining a neutral pH level is a tricky balancing act. If your pool water rates less than seven, it’s too acidic, and a pH of more than seven indicates a base, meaning that it’s too alkaline.
So when you measure pH, you’re assessing how acidic or alkaline your pool water is, based on the substances within the water. However, you don’t measure your pool’s total alkalinity using the pH scale but rather as parts per million (ppm). Even more confusing for pool owners, pH and alkalinity are different although they do have an important relationship. Your pool water’s pH usually reflects its alkalinity level (though that’s not always the case).
Said another way, if your pool water’s pH level is low, it’s likely that its alkalinity is also low. And the opposite is true: if the water’s pH is high, its alkalinity will almost certainly be high as well.
The following may help give you a better sense of acidity versus alkaline:
- Lemon juice has a pH level of approximately 2.0 to 2.5 (highly acidic)
- Orange juice has a pH level of about 3.5 (acidic)
- Tomato juice has a pH level that ranges from 4.1 to 4.6 (acidic)
- Different types of honey have a pH ranging from 3.3 to 6.5 (acidic)
- Most coffees have a pH ranging from 4.85 to 5.1 (acidic)
- Milk has a pH that ranges from 6.5 to 6.7 (slightly acidic to neutral)
- Drinking water has a pH level ranging from 6.5 to 8.5 (neutral)
- Ammonia has a pH of approximately 11.6 (moderately alkaline or basic)
- Bleach is a corrosive cleaning product due to its pH between 11 and 13 (highly alkaline)
Why is Pool Alkalinity Important?
If your pool water has low alkalinity, it has become too acidic. This may cause severe eye, nasal, and skin irritation and also corrode your pool’s equipment, including its plumbing. In contrast, if the water is too alkaline, it may cause scaling of your pool’s plumbing and its surface as well as cloudiness or murkiness of the water.
Further, low or high alkalinity negatively impacts chlorine, which is the most frequently used chemical to keep your pool water free from potentially dangerous bacteria. Chlorine works to clean pools by attacking the fats known as lipids in cellular walls in bacteria and other microorganisms, harming their intracellular structures and enzymes and killing them. (See below for more information on chlorine.)
So what is the ideal pH level for your pool water? You’ll want to aim for close to neutral but slightly alkaline: i.e., 7.4 to 7.6 on the pH scale. Slightly alkaline water will be the kindest to your pool and your skin, eyes, and nose since this is the pH level that enables chlorine to best work its magic.
What is Chlorine?
As noted above, chlorine acts as a chemical sanitizer for your pool. Available in liquid, tablet, or powder form, chlorine cleans your pool water and makes it a safe environment for swimming. In addition to preventing the spread of disease-causing bacteria and other microorganisms, it also fights against the growth of algae and the accumulation of environmental debris and dirt, saliva, and other excretions from adults and children who swim in your pool.
Chlorine is most effective when the pH levels of your pool water are optimal. You’ll therefore want to regularly measure pH levels to ensure your chlorine is doing the best job possible. Keep in mind that sunlight helps chlorine work against microorganisms more quickly. Therefore, if your pool gets a great deal of sun, you’ll go through more chlorine when compared to pools that are primarily in the shade.
What Happens if Pool Alkalinity is Too High or Too Low?
Although you may not initially notice your pool’s low alkalinity level, this will frequently drive down your pool water’s pH level as well. The water will become more acidic, resulting in the following:
- Irritated eyes and dry, itchy skin
- Corrosion of the pool’s metal surfaces, including pipes, screws, and filters
- Staining of your pool’s walls/lining
- pH bounce, meaning quick fluctuation in the pool water’s pH levels
- Cracking and pitting of your pool walls/lining and surfaces
- Decreased effectiveness of chlorine and other pool sanitizers.
High alkalinity is not as damaging as low alkalinity. However, it’s still crucial to keep your pool’s total alkalinity appropriately balanced. Doing so will help to prolong the life of your pool’s filters, pump, and pipes and lower your maintenance costs. High alkalinity and an imbalanced pH level may cause the following:
- Reduced water circulation due to clogged pool filters, pipes, circulation equipment, and heaters
- Water scaling on pool equipment and surfaces
- Cloudy, murky water
- Increased water pressure secondary to pipes narrowing and becoming clogged, causing them to work harder, which may result in cracking and the need to replace your pool pump
- Irritated eyes and nasal passages as well as itchy skin
Low alkalinity will prevent sufficient removal of viruses, bacteria, algae, and other microorganisms, putting swimmers at risk. Your pool water will also become corrosive, causing damage to your pool’s surfaces and equipment.
What Causes pH Level to Rise and Fall?
Many pool owners understandably complain about how difficult it is to maintain an appropriate pH level for their pools. It often seems like just about anything can throw off your pool water’s balance, including rain, leaves, bodily waste, rodents falling into the pool, and other debris.
Increased alkalinity may result from using high-alkalinity water to fill your pool or adding too much chlorine or non-chlorine chemicals to destroy contaminants. It may also develop due to the accumulation of sweat, body lotions, and other excretions in your pool.
Decreased alkalinity may result from rainwater or acid rain that serves to dilute your pool water or bodily fluids from swimmers, such as urine. In addition, because chlorine tablets carry a low pH, allowing too many tablets to dissolve in pool water will also lower the pool’s pH level.
The solution to maintaining your pH level is adding a pH buffer. Think of increasing alkalinity as adding a layer of armor to your pH, absorbing fluctuations, and keeping your pool chemistry stable.
What Is The Right Amount Of Alkalinity?
The right amount of total alkalinity for your pool is between 80 to 120 parts per million, depending on the specific type of chlorine that you use. You can use a swimming pool testing kit to measure the alkalinity of your pool. Your kit determines parts per million (ppm)–i.e., equaling one milligram per liter of water.
How Can You Raise and Lower Alkalinity in Your Pool?
Begin by determining how many gallons your pool holds and the specific ppm level you’d like to obtain. As noted above, the appropriate range is between 80 and 120 ppm, so you’ll want to target the middle of this range. If you don’t know how many gallons of water your pool contains, you can use our pool volume calculator to confirm your pool’s size.
How to Raise Alkalinity
If you need to raise your pool’s total alkalinity, use baking soda (also called sodium bicarbonate) or any alkalinity-increaser product. However, if you choose to use the latter, ensure that the product is made from sodium bicarbonate since that is the main component that increases pH. After you’ve added the baking soda or alkalinity-increaser, allow your pool to settle for six hours, and then retest it.
How to Lower Alkalinity
In contrast, lower your pool’s total alkalinity by using alkalinity-decreaser products, such as sodium bisulfate (also called dry acid) or muriatic acid. After you’ve followed the products’ directions and added the dry acid, muriatic acid, or other alkalinity-decreaser product, check your pool water’s pH level to ensure it’s now in the proper range.
I’ve linked my articles above for raising and lowering your pool’s alkalinity levels in case you want to check those out. You can also use my pool alkalinity calculator to help you out.
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The bottom line: You don’t have to be a chemist or a chemistry major to keep your pool sparkling clean. Simply follow the suggestions above, and your beautiful pool will make your backyard the most popular spot in your neighborhood.
Questions? Let me know.