How to Adjust Total Alkalinity in Gunite Pools

Maintaining the perfect balance of water chemistry is essential for the longevity and enjoyment of any gunite pool. One of the critical factors in achieving this balance is managing the total alkalinity of your pool water.

Total alkalinity plays a pivotal role in stabilizing the pH levels, ensuring that they remain within the ideal range for swimming and protecting your pool equipment.

In this comprehensive guide, we’ll delve into the importance of total alkalinity in gunite pools and provide you with step-by-step instructions on how to adjust it effectively.

Whether you’re a seasoned pool owner or just diving into the world of gunite pools, understanding and managing total alkalinity is a fundamental skill that can make a significant difference in the quality and maintenance of your pool.

Understanding Total Alkalinity

Before we delve into the practical aspects of adjusting total alkalinity in your gunite pool, it’s essential to grasp the concept and significance of total alkalinity in pool water chemistry.

What is Total Alkalinity

Total alkalinity, often abbreviated as TA, is a measure of the water’s ability to resist changes in pH levels. In simpler terms, it acts as a buffer that helps stabilize the pH of your pool water. When total alkalinity is within the recommended range, it prevents the pH level from fluctuating too drastically, which is vital for the comfort and safety of swimmers and the overall health of your pool.

Why is Total Alkalinity Important

Maintaining proper total alkalinity is crucial for several reasons:

• pH Stability: Total alkalinity acts as a pH stabilizer, preventing the pool water from becoming too acidic or too alkaline. This stability ensures that the water is comfortable for swimmers and extends the life of your pool equipment.
• Water Clarity: When total alkalinity is within the ideal range, it helps prevent cloudy or hazy water, contributing to a crystal-clear pool that’s inviting to swim in.
• Corrosion and Scaling: Imbalanced total alkalinity can lead to corrosion of pool surfaces and equipment or the formation of scaling deposits. Maintaining the right level helps prevent these issues.
• Efficient Chlorination: Proper TA levels enhance the effectiveness of your pool’s sanitizer, such as chlorine. This ensures that your pool water remains safe and free from harmful microorganisms.

Ideal Total Alkalinity Range for Pools

The ideal total alkalinity (TA) range for most swimming pools, including gunite pools, typically falls between 80 and 120 parts per million (ppm). This range provides a good balance between pH stability and water clarity while also preventing potential issues like corrosion and scaling.

Here’s a breakdown of what different TA levels can mean:

• Below 80 ppm: If total alkalinity falls below 80 ppm, your pool water can become prone to pH fluctuations. This can lead to problems like corrosive water, eye and skin irritation for swimmers, and potential damage to pool surfaces and equipment.
• 80 to 120 ppm (Ideal Range): Maintaining total alkalinity within this range helps stabilize the pH level of your pool water. It provides a buffer against rapid pH changes and ensures a comfortable swimming environment with clear water.
• Above 120 ppm: When TA levels exceed 120 ppm, the water can become too alkaline. This can lead to issues like scaling, cloudy water, and reduced effectiveness of pool sanitizers. Swimmers may also experience skin and eye discomfort.

Relationship Between Alkalinity and pH Levels

These two parameters are closely connected and play a significant role in pool chemistry. Here’s how they are related:

Buffering Capacity: Total alkalinity acts as a buffer in pool water. This means it helps to stabilize the pH level by resisting rapid fluctuations. When TA is within the recommended range (typically 80-120 ppm), it prevents the pH from becoming too acidic (low pH) or too alkaline (high pH).

pH Increase: If the pH level in your pool starts to drop (become more acidic), proper total alkalinity acts as a buffer to slow down this decrease. Without adequate TA, the pH can rapidly drop, making the water corrosive and uncomfortable for swimmers.

pH Decrease: Conversely, if the pH level begins to rise (become more alkaline), the total alkalinity can act as a buffer to slow down this increase. Elevated pH levels can lead to issues like scaling and cloudy water. Adequate TA helps prevent such problems.

Maintaining Balance: To maintain the right balance between TA and pH, it’s essential to regularly test both parameters and make adjustments as needed. If the pH is consistently too high, you may need to lower it with the addition of an acid like muriatic acid. If the pH is consistently too low, you may need to raise it using a pH increaser. Proper total alkalinity can help these adjustments be more effective and stable.

How to Test Pool Alkalinity

Testing pool alkalinity (Total Alkalinity or TA) is a straightforward process that can be done using a pool water testing kit or test strips. Here are the steps to test the alkalinity of your pool:

Collect a Water Sample: Use a clean container or the testing vial provided in your testing kit. Submerge the container or vial below the water’s surface to a depth of about 18 inches (45 cm). Collect enough water to fill the testing vial or reach the required fill line specified in your testing kit’s instructions.

Add the Reagent: If you’re using a liquid testing kit, follow the manufacturer’s instructions to add the appropriate reagent for testing alkalinity. For test strips, this step is not required.

Stir the Water: Use a clean plastic or glass stirring rod to gently mix the water sample for about 10-15 seconds. This ensures that any added reagent is thoroughly mixed with the pool water.

Wait for Color Change: Depending on the type of test kit or strips you’re using, you may need to wait a specific amount of time for the color to change. Follow the manufacturer’s instructions for the recommended waiting time.

Read the Results: After the specified waiting time, observe the color change in the water or on the test strip. Compare the color of the water or strip to the color chart provided in your testing kit.

Determine Alkalinity Level: The color chart will have a range of colors representing different alkalinity levels in parts per million (ppm). Match the color of your test sample to the closest color on the chart to determine the alkalinity level.

Record the Alkalinity Level: Take note of the alkalinity reading, which is typically expressed in ppm.

Interpret the Results: Compare the recorded alkalinity level to the recommended range for your pool (usually 80-120 ppm). If the alkalinity falls outside this range, you may need to make adjustments.

Frequency of Testing

The frequency of testing pool alkalinity (Total Alkalinity or TA) and other water parameters depends on several factors, including the size of your pool, its usage, and the local climate. Here are some general guidelines for how often you should test pool alkalinity:

• At the Start of the Season: At the beginning of the swimming season, it’s essential to test all water parameters, including alkalinity, to ensure a balanced and safe swimming environment. This initial test provides a baseline for your pool’s chemistry.
• Weekly Testing: During the peak swimming season, it’s advisable to test your pool water at least once a week. Regular testing helps you catch and address any chemical imbalances or issues promptly.
• After Significant Rainfall: After heavy rainfall or storms, it’s a good practice to test your pool water. Rainwater can affect the pool’s chemistry by diluting chemicals and altering pH and alkalinity levels.
• After Adding Chemicals: Whenever you add pool chemicals, such as pH adjusters or alkalinity increasers, it’s important to retest the water after a few hours to ensure that the levels are within the desired range.
• After High Bather Load: If you’ve had a large number of swimmers in your pool or hosted a pool party, it’s a good idea to test the water afterward. High bather load can impact the pool’s chemistry.
• During Hot Weather: In regions with hot and sunny weather, evaporation can concentrate the chemicals in the pool water. Periodic testing can help you maintain proper levels.
• Monthly Maintenance: Even if your pool is not in use during the offseason or winter months, consider testing the water at least once a month to ensure it remains balanced.
• As Needed: If you notice any signs of water imbalance, such as cloudy water, eye or skin irritation, or equipment issues, test the water immediately to identify and address the problem.

Causes of Total Alkalinity Imbalance

When the total alkalinity is out of balance (either too high or too low), it can have negative effects on the pool and its users. Let’s explore the causes for imbalances in total alkalinity:

Causes of Low Total Alkalinity

• Acid Addition: Excessive addition of muriatic acid or dry acid (sodium bisulfate) to lower pH can also inadvertently lower TA.
• Rainwater: Rain can be slightly acidic (especially acid rain), and excessive rainwater entering the pool can reduce the TA.
• Fill Water: If the source water used to fill the pool has low alkalinity, it can reduce the TA of the pool.
• Draining and Refilling: Draining a portion of the pool and refilling it with low TA water can reduce the overall TA.
• Organic Contamination: Leaves, grass, and other organic materials can introduce acids to the pool, reducing TA.

Causes of High Total Alkalinity

• Alkaline Fill Water: Using source water with high TA to fill or top up the pool can increase the pool’s TA.
• Excessive Use of Baking Soda: Sodium bicarbonate (baking soda) is often used to raise TA. Overuse can lead to excessively high TA.
• Chemical Imbalance: Overuse of certain pool chemicals, especially those designed to raise pH, can inadvertently increase TA.
• Improper Chemical Addition: Not following recommended dosages or frequent additions without testing can result in high TA.
• Evaporation: As water evaporates, it can concentrate the minerals and chemicals in the pool, potentially increasing TA.

Implications of Total Alkalinity Imbalance

Maintaining the correct TA is crucial for pool health for several reasons. Let’s delve into the implications of imbalanced TA:

pH Instability: TA acts as a buffer for pH. If the TA is too low, the pH level can fluctuate widely with even small additions of acid or base. Conversely, if the TA is too high, it can be challenging to adjust the pH.

Corrosion & Erosion:

• Low TA: Water becomes corrosive, which can lead to metal corrosion (like pool equipment, ladders, etc.) and erosion of pool surfaces, especially plaster finishes. This can lead to staining and pitting of the pool’s surface.
• High TA: While not directly corrosive, high TA can cause scale formation when combined with high pH and high calcium hardness.

Calcium Scaling: High TA can contribute to calcium carbonate coming out of solution, which forms scale. This scale can deposit on pool surfaces, clog filters, and reduce the efficiency of heaters.

Cloudy Water: Imbalanced TA can make it harder to keep water clear. High TA can lead to cloudy water, especially when combined with high calcium hardness and pH.

Sanitizer Efficiency: The efficiency of chlorine, the most common pool sanitizer, is affected by the pH of the water. Since TA influences pH stability, an imbalanced TA can indirectly impact the effectiveness of the sanitizer.

Irritation to Swimmers: Drastic imbalances in TA can lead to water that is uncomfortable for swimmers. Low TA (and resulting low pH) can cause eye and skin irritation.

Increased Chemical Usage: Trying to correct and stabilize the pH in a pool with imbalanced TA often requires more chemicals. This not only increases the cost of maintaining the pool but can also lead to over-saturation of other chemicals.

Equipment Damage: Low TA can lead to corrosion of pool equipment, which can reduce its lifespan and functionality. On the other hand, high TA, leading to scale formation, can reduce the efficiency of heaters and clog pool filters.

Complicates Water Balance: TA is one of the factors in the Langelier Saturation Index (LSI), a tool used to predict whether water will deposit calcium scale or dissolve calcium from surfaces. An imbalanced TA can skew the LSI, making it harder to achieve balanced water.

How to Lower Total Alkalinity in Pool

Lowering total alkalinity (TA) in a pool or spa is essential when TA levels are too high. Excessive TA can lead to problems such as cloudy water, scale formation, and reduced chlorine effectiveness. Here are some methods to lower the total alkalinity in a pool:

Using Muriatic Acid (Hydrochloric Acid): Muriatic acid is a common chemical used to lower TA in pools. Before adding muriatic acid, make sure the pool’s pH is above 7.0. Slowly pour the acid along the pool’s deep end. Allow the pump to run for at least 30 minutes to distribute the acid. Retest TA after a few hours and adjust as needed.

Using Sodium Bisulfate (Dry Acid): Dry acid can also be used to decrease TA. It’s a granular form of acid that is safer to handle than muriatic acid. Like with muriatic acid, make sure the pool’s pH is above 7.0 before adding. Distribute the dry acid around the deep end of the pool. Run the pump for at least 30 minutes. Retest TA after a few hours and adjust as needed.

Aeration: Aeration can help to increase the pH without significantly impacting the TA. This is useful if you’ve added acid to reduce TA but now need to raise the pH without raising the TA. Methods of aeration include water features, air stones, and even pointing pool return jets upwards to agitate the surface.

Partial Drain and Refill: Sometimes, the best approach to lower TA is to partially drain the pool and then refill it with fresh water that has a lower TA. This is a more drastic measure but can be effective if other methods are not bringing down the TA to the desired levels.

Use of Specialized Chemicals: Some specialized pool chemicals on the market are designed to specifically lower TA without significantly impacting the pH. Always follow the manufacturer’s instructions when using these products.

Carbon Dioxide (CO2) Injection: Injecting CO2 into pool water will form carbonic acid, which can lower both pH and TA. This method is more commonly used in commercial settings due to the equipment required. Over time, the pH will tend to rise again (due to the natural off-gassing of CO2), but the TA will remain lower.

Using Alkalinity Reducers: There are commercial products specifically designed to reduce TA. These products typically contain acids in a form that targets TA more than pH. Always follow the manufacturer’s instructions.

Adjusting the Fill Water: If the source of your fill water has high TA, consider using a water softener or another treatment system to adjust the TA of the fill water before adding it to the pool.

Control of Return Jets: Pointing the return jets downwards can help reduce surface agitation, which in turn can help minimize the rise in pH that often accompanies efforts to lower TA.

Consideration of Borates: Some pool professionals use borates (usually in the form of borax) as a buffer in the water. This can help stabilize the pH, making it easier to manage TA without seeing wild swings in pH.

Natural Waters: Natural waters like rainwater typically have a lower TA. If you’re in an area with frequent rain, letting rainwater dilute the pool water can help lower TA. However, be cautious about other potential water imbalances this might introduce.

Use of Reverse Osmosis (RO): RO systems can be used to treat pool water, removing high levels of TA and other unwanted chemicals. This method is more expensive and is usually reserved for severe water imbalance issues or for pools in areas with very hard water.

How to Raise Total Alkalinity

If the TA is too low, it can cause the pH level to fluctuate dramatically, leading to various problems like corrosion of pool equipment, staining, and discomfort for swimmers. To raise the total alkalinity in pools, the most common methods involve adding chemicals that can contribute alkaline substances to the water. Here are some methods:

Baking Soda (Sodium Bicarbonate): Sodium bicarbonate is the most common and cost-effective way to raise total alkalinity. You can slowly add baking soda to the pool while the pump is running to ensure even distribution. It’s recommended to add it in small amounts and test the water after each addition to avoid overshooting the desired TA level.

Soda Ash (Sodium Carbonate): Soda ash will raise both the pH and the total alkalinity. If you only need to raise the TA and not the pH, it’s better to use baking soda. Like with baking soda, it should be added slowly with the pump running.

Commercial Alkalinity Increasers: These are typically made from sodium bicarbonate or sodium carbonate. They come with instructions on the amount to add based on the volume of your pool and the desired increase in TA.

Aeration: Aeration can help to increase the pH of the water, which can indirectly increase the total alkalinity over time. This method involves introducing air into the water, which drives off carbon dioxide. As carbon dioxide levels decrease, the pH rises.

Calcium Hydroxide (Lime): This method is less common for residential pools, but calcium hydroxide can be used to increase both pH and total alkalinity. It’s important to be cautious when using lime, as it can easily lead to an overshoot in pH and TA levels.

Borax (Sodium Borate): Borax can be used to raise the pH of pool water without having as much of an impact on total alkalinity. However, when the pH increases, it can subsequently lead to a slow increase in total alkalinity. It’s important to be cautious when using borax and to ensure that borate levels in the pool don’t become too high.

Potassium Bicarbonate: This is an alternative to sodium bicarbonate and can be used to raise total alkalinity. It’s less common than baking soda but can be particularly useful in situations where sodium intake needs to be minimized, such as in certain saltwater pools.

Automatic pH and Alkalinity Controllers: Some modern pool systems come equipped with automatic controllers that can monitor and adjust the pH and total alkalinity of the water. These systems usually involve dosing the pool with chemicals as needed to maintain balance.

Natural Minerals and Materials: Some natural materials, like certain types of rocks or minerals, can slowly leach alkaline substances into water. Though not a method one would use to deliberately adjust alkalinity in the short term, being aware of the materials in and around your pool can help you understand and predict changes in water chemistry.

Alkaline Water Ionizers: These are devices that can raise the pH and total alkalinity of water by electrolysis. While more common for drinking water treatment, there are larger systems that could theoretically be used for pools, though they are not standard.

Common Mistakes to Avoid When Adjusting Total Alkalinity

Adjusting total alkalinity (TA) in a pool is an essential part of maintaining proper water balance. However, there are common mistakes that pool owners can make when trying to adjust TA levels. Here are some of the common mistakes to avoid:

Not Testing Before Adjustment: Failing to test the current TA level before making adjustments is a common mistake. It’s crucial to know the starting point to determine the appropriate action needed.

Overdosing with Chemicals: Adding too much alkalinity increaser, such as sodium bicarbonate or baking soda, at once can lead to overshooting the desired TA level. Always follow dosage recommendations based on your pool’s size and the calculated needs.

Ignoring pH Levels: TA and pH levels are closely related. Adjusting TA without considering its impact on pH can lead to unintended pH swings. Always monitor and adjust pH levels concurrently when working with TA.

Not Properly Dissolving Chemicals: Adding chemicals directly to the pool without dissolving them in water first can result in uneven distribution and localized high TA levels. Dissolve chemicals in a bucket of water before adding them to the pool.

Not Waiting for Testing Results: Some pool owners add chemicals and immediately retest the water. It’s essential to allow time for the chemicals to circulate and equilibrate before retesting. Follow the manufacturer’s recommendations for waiting times.

Not Testing After Adjustment: After making adjustments, some pool owners forget to retest the TA levels to ensure they have reached the desired range. Regular testing is crucial to verify that the adjustment was successful.

Ignoring the Pool’s Unique Factors: Each pool is different, and factors like pool size, water temperature, bather load, and local water source can affect TA levels. Don’t assume that a one-size-fits-all approach will work for your pool.

Relying Solely on Commercial Products: While commercial products can be effective, solely relying on them without understanding the chemistry behind the adjustment can lead to imbalances or unnecessary expenses. Educate yourself about pool chemistry.

Not Seeking Professional Advice: If you’re unsure about how to adjust TA or if your pool has complex chemistry issues, it’s a mistake not to seek guidance from a pool professional or water chemistry expert. They can provide personalized recommendations.

Making Hasty Corrections: Avoid making large and hasty adjustments to TA levels. Gradual adjustments are safer and minimize the risk of overcorrection.

Neglecting Regular Maintenance: TA levels can change over time due to factors like rainfall, water additions, or chemical use. Neglecting regular testing and maintenance can lead to imbalances.

Conclusion

Maintaining the total alkalinity in your gunite pool is crucial for ensuring the water’s balance, comfort, and overall longevity of the pool’s structure. By regularly testing and adjusting the alkalinity levels within the recommended range, you can prevent issues such as pH fluctuations and corrosion of pool equipment.

Remember to use the appropriate chemicals, follow manufacturer guidelines, and consult with a professional if you’re unsure about the proper adjustments. With diligence and care, you can enjoy a pristine and well-balanced gunite pool for years to come.

Frequently Asked Questions