How to Balance Hardness Levels in Gunite Pool?

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Maintaining proper calcium hardness levels is crucial for the health and longevity of a gunite pool. Calcium hardness refers to the amount of dissolved calcium in the pool water. It plays a vital role in balancing the water chemistry, preventing both corrosive and scaling effects on pool surfaces.

Gunite pools, which are constructed using a concrete mixture, require specific attention to calcium hardness levels. Unlike vinyl or fiberglass pools, gunite pools can withstand higher calcium hardness levels without suffering damage.

Properly balanced water chemistry in a gunite pool ensures that the pool surfaces remain in optimal condition. It also prevents cloudiness, staining, and other surface problems caused by calcium sediment or excessive hardness in the water.

In this guide, we will delve into the importance of understanding and managing calcium hardness in gunite pools. We will discuss testing and monitoring techniques, as well as methods for both increasing and decreasing calcium hardness levels. By following these guidelines, pool owners can enjoy a well-maintained pool that provides a safe and enjoyable swimming experience.

Key Takeaways

  • Calcium hardness levels are crucial for the health and longevity of a gunite pool, as it prevents corrosion and scaling on pool surfaces.

  • Gunite pools can handle higher calcium hardness levels compared to vinyl or fiberglass pools due to their durable and non-porous nature.

  • The optimal range for calcium hardness in gunite pools is typically between 200 and 400 ppm, though manufacturer recommendations may vary.

  • Imbalances in calcium hardness can occur due to factors such as water source, chemical additions, evaporation, pH, alkalinity imbalances, and pool maintenance.

  • High calcium hardness can lead to scaling, cloudy water, equipment damage, and surface problems, while low calcium hardness can cause corrosion, etching, pH instability, and water imbalance.

  • Regular testing and monitoring of calcium hardness are essential to prevent these issues and maintain a balanced pool environment.

  • Testing methods include test kits (strips or liquid reagents) and electronic testers for accurate measurements.

  • The frequency of testing calcium hardness is typically once a month, with additional testing after new fills, water changes, seasonal changes, or unusual water conditions.

  • Best practices for accurate readings involve calibrating and maintaining testing equipment, using fresh and clean water samples, testing under optimal conditions, and following test kit instructions carefully.

  • Raising calcium hardness can be achieved using calcium hardness increasers, while lowering high levels can be done through partial water replacement, complete water replacement, sequestering agents, flocculants, or combination methods.

  • It is important to follow manufacturer guidelines, prevent overcorrection, consider total dissolved solids (TDS), dilute increasers as directed, take safety precautions, and monitor the pool regularly when adjusting calcium hardness levels.

Understanding Calcium Hardness

Calcium hardness refers to the concentration of dissolved calcium ions in the pool water. It is an important aspect of water chemistry in gunite pools. Calcium is naturally present in water sources, and its levels can vary depending on the water supply.

The role of calcium hardness in gunite pools is multi-fold.

  • Firstly, it helps to prevent corrosion of pool surfaces such as the concrete shell, metal fittings, and equipment. The proper level of calcium hardness acts as a protective barrier, reducing the chances of damage caused by corrosive water.

  • Secondly, calcium hardness plays a significant role in preventing scaling. When the pool water becomes oversaturated with calcium, it can lead to the precipitation of calcium carbonate, resulting in the formation of scale on pool surfaces, plumbing lines, and equipment. This can lead to reduced water flow, clogged filters, and other operational issues.

  • Additionally, calcium hardness contributes to the overall water balance of the pool. It impacts the effectiveness of sanitizers like chlorine and bromine, as well as the pH stability of the water. Imbalances in calcium hardness levels can lead to chemical fluctuations, affecting the water clarity and comfort of swimmers.

Optimal Range for Calcium Hardness in Gunite Pools

The optimal range for calcium hardness in a gunite pool typically falls between 200 and 400 parts per million (ppm). This range provides a good balance between preventing corrosion and scaling. It is important to note that the exact range may vary depending on the specific needs of the pool and the manufacturer’s recommendations.

Compared to other pool types like vinyl or fiberglass, gunite pools can tolerate higher levels of calcium hardness. Vinyl and fiberglass pools generally require lower levels of calcium hardness, typically ranging from 150 to 250 ppm. This is because the pool surfaces in vinyl and fiberglass pools are more susceptible to damage from high calcium levels.

The reason gunite pools can handle higher calcium hardness levels is due to the durable and non-porous nature of the concrete material. However, it is still important to stay within the recommended range to avoid any potential issues.

Maintaining the optimal calcium hardness range is essential for gunite pools. It helps protect the pool’s structural integrity by preventing corrosion, while also reducing the risk of scaling on surfaces and equipment. By regularly testing and adjusting calcium hardness levels as needed, gunite pool owners can ensure the longevity of their pool and enjoy a comfortable swimming experience.

Causes of Hardness Imbalance

Imbalances in calcium hardness levels in a gunite pool can occur due to a variety of factors. Here are some common causes of hardness imbalances:

  • Water Source: The source of the water being used to fill the pool can have a significant impact on calcium hardness levels. Different water sources have varying levels of dissolved minerals, including calcium. If the water source has naturally high calcium levels, it can contribute to high calcium hardness in the pool. Conversely, water sources with lower calcium content may result in lower hardness levels.

  • Chemical Additions: Improper or excessive use of certain chemicals can also lead to hardness imbalances. For example, adding excessive amounts of calcium-based products, such as calcium chloride increasers, can cause an increase in calcium hardness. Similarly, using water-balancing chemicals without considering the pool’s current calcium hardness levels can lead to imbalances.

  • Evaporation and Dilution: As water evaporates from the pool, the mineral content, including calcium, remains in the pool and becomes more concentrated. If water is regularly topped up without considering the impact on calcium hardness, it can lead to increasing levels over time. Conversely, if there is a significant dilution of the pool water, such as through heavy rain or large volume water changes, it can result in lower calcium hardness levels.

  • pH and Alkalinity Imbalances: Imbalances in pH and alkalinity can indirectly impact calcium hardness levels. High pH and alkalinity can cause an increase in calcium carbonate precipitation, leading to scaling and higher calcium hardness levels. Conversely, low pH and alkalinity can result in the dissolution of calcium carbonate, causing the calcium hardness to decrease.

  • Pool Maintenance and Equipment: Poor pool maintenance practices, such as inadequate filtration, inadequate brushing or cleaning, or malfunctioning equipment, can contribute to hardness imbalances. Insufficient filtration and cleaning can lead to the accumulation of calcium deposits, resulting in high hardness levels. Malfunctioning equipment, such as faulty heaters or chemical feeders, can also affect water chemistry and contribute to imbalances.

Consequences of Hardness Imbalance

Having high or low calcium hardness levels in a gunite pool can both lead to various consequences and issues that pool owners should be aware of. Let’s explore the impacts of high and low calcium hardness levels in more detail:

Consequences of High Calcium Hardness

  • Scaling: When calcium levels become too high, the water becomes oversaturated with calcium, leading to the formation of scale on pool surfaces, plumbing lines, and equipment. This can cause reduced water flow, clogged filters, and increased maintenance requirements.

  • Cloudy Water: High calcium hardness levels can contribute to cloudy or hazy water. The excessive calcium can react with other chemicals in the water, causing them to bind together and form particles that make the water appear cloudy.

  • Equipment Damage: The buildup of scale caused by high calcium hardness can damage pool equipment such as heaters, pumps, and filters. Scale can clog the equipment, reduce efficiency, and potentially lead to expensive repairs or replacements.

  • Surface Problems: High calcium hardness levels can result in calcium deposits on pool surfaces and fixtures, causing unsightly stains and discoloration. These deposits can be difficult to remove and may require professional cleaning or resurfacing.

Consequences of Low Calcium Hardness

  • Corrosion: Insufficient calcium hardness in the pool water can make it more corrosive, leading to damage to pool surfaces, metal fittings, and equipment. This can weaken the pool structure and shorten the lifespan of various components.

  • Etching: Water with low calcium hardness can erode and etch the pool surfaces, particularly the plaster or gunite. This can result in rough and pitted surfaces that are uncomfortable for swimmers and require costly repairs or resurfacing.

  • pH Instability: Low calcium hardness can cause pH levels to fluctuate more frequently. When pH is not properly balanced, it can lead to ineffective sanitization, eye and skin irritation, and other water quality issues.

  • Water Imbalance: Low calcium hardness can disrupt the overall water balance, affecting the effectiveness of other chemicals such as sanitizers and pH adjusters. This can lead to additional chemical adjustments and increased maintenance efforts.

Maintaining proper calcium hardness levels is vital to prevent these issues and ensure the longevity of a gunite pool. Regular testing and appropriate adjustments can help keep the calcium hardness within the recommended range, promoting a balanced and well-maintained pool.

Testing and Monitoring Calcium Hardness

Regular testing for calcium hardness is of utmost importance, especially in gunite pools, to ensure the water chemistry remains balanced. Here are some key reasons why regular testing for calcium hardness is crucial:

  • Prevents Surface Damage: Gunite pool surfaces are constructed using a porous concrete mixture. Regular testing allows pool owners to monitor calcium hardness levels and prevent them from getting too low, which could lead to corrosive water. With proper calcium hardness levels, the risk of surface damage and deterioration is minimized, ensuring the longevity and integrity of the pool structure.

  • Helps Prevent Scaling: Testing for calcium hardness allows pool owners to detect and address high calcium levels. High calcium hardness can result in scaling, where calcium deposits form on pool surfaces, plumbing lines, and equipment. By regularly testing and maintaining proper calcium hardness levels, pool owners can prevent the buildup of scale and avoid costly repairs or replacements of equipment.

  • Ensures Effective Chemical Balance: Calcium hardness plays a role in the overall chemical balance of the pool water. Testing allows pool owners to understand the impact of calcium hardness on pH levels, the effectiveness of sanitizers, and the overall water clarity. By maintaining the proper calcium hardness levels, other chemicals can work more efficiently, reducing the need for constant adjustments and providing a more comfortable swimming experience.

  • Promotes Water Clarity: Imbalances in calcium hardness can contribute to cloudy or hazy water. Regular testing allows pool owners to identify and address any fluctuations in calcium hardness levels promptly. By maintaining optimal calcium hardness, pool water remains clear and visually appealing.

  • Optimizes Water Comfort: Proper calcium hardness levels contribute to the comfort of swimmers. Water with balanced calcium hardness feels more pleasant on the skin and eyes, reducing irritation and discomfort that can arise from imbalances. Regular testing helps ensure that the water remains comfortable and enjoyable for swimmers of all ages.

Various Testing Methods

There are multiple testing methods available to measure calcium hardness levels in gunite pools. Here are some commonly used methods:

Test Kits

Test kits are widely available and offer a convenient and cost-effective way to test calcium hardness levels. They typically include test strips or liquid reagents that are added to a water sample, resulting in a color change that indicates the calcium hardness level. Test kits often measure calcium hardness in parts per million (ppm) and provide a straightforward method for pool owners to test and monitor their water chemistry.

Cost-effective and widely availableMay not provide the highest level of accuracy
Easy to use with straightforward instructionsColor interpretation may vary between users
Portable and convenient for on-the-spot testingLimited testing capabilities for other water parameters

Electronic Testers

Electronic testers, also known as digital or electronic meters, provide a more advanced and accurate method for testing calcium hardness. These devices use electrodes to measure the concentration of calcium ions in the water sample and display the results digitally. Electronic testers often offer additional features and can be used to measure other water parameters such as pH, chlorine levels, and total alkalinity.

Accurate and precise measurementsHigher initial cost compared to test kits
Digital display for easy readingRequires calibration and occasional maintenance
Can measure multiple water parametersMay need occasional battery replacement
Suitable for pool owners who prefer advanced technologyRequires proper care and storage to maintain accuracy

Professional Testing

For those who prefer a hands-off approach or want more accurate and comprehensive testing, professional water testing services are available. Local pool supply stores or certified pool professionals often offer water testing services using specialized equipment and methods. Professionals can provide detailed results, offer recommendations for corrective actions, and assist in maintaining proper water balance.

Highly accurate and comprehensive testingRequires reliance on external testing services
Professional analysis and guidanceAdditional cost for each testing service
Can provide recommendations for corrective actionsMay require waiting for test results before taking action
Ideal for pool owners who prefer a hands-off approachLimited availability and may require travel to testing site

How Frequently to Test Calcium Hardness?

The frequency of testing calcium hardness in a gunite pool can vary depending on factors such as water source, pool usage, and seasonality. A general guideline is to test calcium hardness levels once a month. However, certain circumstances may warrant more frequent testing. Here are some scenarios when more frequent testing may be necessary:

  • New Fills or Water Changes: After adding fresh water to the pool, whether it’s a new fill or a significant water change, it is a good practice to test calcium hardness levels. This helps ensure that the new water is within the desired range and does not significantly impact the overall water balance.

  • Seasonal Changes: Seasonal fluctuations, such as temperature changes and higher bather loads during the summer, can impact calcium hardness levels. Testing calcium hardness at the start of each season can help identify any changes and allow for adjustment if needed to maintain proper water balance.

  • Unusual Water Conditions: If you notice sudden changes in water clarity, staining, scaling, or other water quality issues, it is recommended to test calcium hardness levels. This can help identify any imbalances that may be causing the problems and allow for appropriate adjustments to prevent further issues.

  • Other Water Chemistry Adjustments: When making adjustments to other water chemistry parameters, such as pH or total alkalinity, it is a good idea to test calcium hardness levels simultaneously. These factors are interconnected, and making changes to one parameter can affect others. Ensuring that calcium hardness remains within the desired range helps maintain overall water balance.

Remember, these guidelines are general recommendations, and it is important to consider your specific pool’s needs and consult with a pool professional if you have any concerns. Regular testing of calcium hardness is essential for maintaining proper water balance and preserving the integrity of your gunite pool.

Best Practices for Accurate Readings

To ensure accurate readings when testing calcium hardness in a gunite pool, it is important to follow these best practices:

  • Calibrate and Maintain Testing Equipment: If using electronic testers or meters, make sure to calibrate them according to the manufacturer’s instructions. Regularly check the condition of electrodes, replace batteries when needed, and store the equipment properly to maintain accuracy.

  • Use Fresh and Clean Water Samples: Collect water samples for testing from a depth of about 18 inches (45 cm) below the surface of the pool. Avoid areas near return jets or skimmers, as they may not accurately represent the overall pool water. Rinse the container with the pool water before collecting the sample to avoid any contaminants that could affect the test results.

  • Test Water at Optimal Conditions: Test the water under normal operating conditions, preferably when the pool has been running and circulating for at least one hour. Testing when the water is still or stagnant may not provide accurate results. Additionally, ensure that the water temperature is within the optimal range specified by the test kit or testing equipment, as extreme temperatures can affect accuracy.

  • Follow Test Kit Instructions Carefully: Whether using test strips or liquid reagents, carefully read and follow the instructions provided with the test kit. Pay attention to the recommended sample size, reaction times, and any other specific guidelines to obtain accurate results.

  • Store Test Kits Properly: Proper storage of test kits is essential to maintain their accuracy. Ensure that test strips or liquid reagents are stored in a cool and dry place, away from direct sunlight or extreme temperatures. Follow any specific storage instructions provided by the manufacturer to ensure the longevity and accuracy of the test kit components.

  • Repeat the Test for Confirmation: To ensure accuracy, it is a good practice to repeat the test two or three times to confirm the results. If the readings consistently show a significant difference from what is expected, it may indicate the need for additional testing or professional assistance to verify the accuracy of the results.

By following these best practices, pool owners can obtain accurate readings of calcium hardness levels in their gunite pools. Accurate testing is essential for maintaining proper water balance and making informed decisions about any necessary adjustments to the pool’s calcium hardness levels.

Raising Calcium Hardness in Gunite Pools

Raising calcium hardness levels in a gunite pool can be achieved by using calcium hardness increasers, such as calcium chloride. Here’s a step-by-step process to effectively raise calcium hardness levels in a gunite pool:

  • Test Calcium Hardness: Begin by testing the current calcium hardness levels in the pool water using a reliable test kit. This will give you a baseline reading and help determine the amount of calcium hardness increaser needed.

  • Calculate the Amount Needed: Refer to the manufacturer’s instructions on the calcium hardness increaser packaging to determine the amount required to raise the calcium hardness to the desired level. This will typically be measured in pounds or ounces based on the volume of your pool.

  • Preparing the Increaser: Carefully follow the manufacturer’s instructions to prepare the calcium hardness increaser. This may involve diluting the product in a clean bucket of water before adding it to the pool. Always wear appropriate protective gear, such as gloves and eye protection, when handling chemicals.

  • Add the Increaser to the Pool: Slowly pour the calculated amount of calcium hardness increaser into the pool. It is important to spread it evenly across the pool surface while the circulation system is running. This will help distribute the increaser throughout the water and prevent localized areas of high calcium hardness.

  • Brush and Circulate: After adding the calcium hardness increaser, use a pool brush to brush the pool surfaces and encourage uniform mixing. Allow the pool’s circulation system to run for at least 24 hours to ensure thorough distribution of the increaser.

  • Retest and Adjust if Needed: After 24 hours, retest the calcium hardness levels using a reliable test kit. If the desired calcium hardness range has not been reached, additional increments of the calcium hardness increaser may be required. Repeat the process of adding the increaser, brushing, and circulating as needed until the desired calcium hardness is achieved.

  • Monitor and Maintain: Once the desired calcium hardness level is achieved, continue to monitor the levels regularly to ensure they stay within the recommended range. This includes regular testing and adjustments if necessary, especially after water additions or significant changes in pool usage.

Potential Risks and Precautions to Consider

When raising calcium hardness levels in a gunite pool, there are a few potential risks and precautions to consider. Understanding these factors will help ensure a safe and successful process:

  • Follow Manufacturer’s Guidelines: Always read and follow the manufacturer’s instructions for the calcium hardness increaser product you are using. This includes recommended dosage, handling procedures, and safety precautions. Different brands or products may have specific instructions, so it is important to adhere to them for optimal results.

  • Avoid Overcorrection: It is essential not to oversaturate the water with calcium hardness increasers. Adding too much calcium chloride or other increasers can lead to excessive calcium levels, resulting in scaling and other water quality issues. Follow the guidelines provided by the manufacturer and adjust the dosage accordingly to prevent overcorrection.

  • Prevent Chemical Imbalances: Increasing calcium hardness levels can impact the overall water balance of the pool. Calcium hardness levels can influence pH levels, alkalinity, and other chemical parameters. Regularly test and adjust pH and alkalinity as needed to maintain proper water balance throughout the process. It may be necessary to make pH adjustments with the use of pH increasers or decreasers.

  • Consider Total Dissolved Solids (TDS): Raising calcium hardness levels may also increase the total dissolved solids in the pool water. High TDS levels can affect water clarity and potentially lead to other issues. If your pool has high TDS levels, it may be necessary to partially drain and refill the pool water to reduce TDS and maintain overall water quality.

  • Dilute Increasers as Directed: Some calcium hardness increasers, such as calcium chloride, may require dilution before adding them to the pool water. Be sure to follow the dilution instructions provided by the manufacturer to avoid adding concentrated chemicals directly to the pool, which could cause localized high calcium levels or other problems.

  • Safety Precautions: When handling calcium hardness increasers or any other chemicals, always take appropriate safety precautions. Wear gloves, protective eyewear, and clothing to avoid direct contact with the chemicals. Store chemicals in a cool, dry, and secure location, away from children and pets.

  • Test and Monitor Regularly: After raising calcium hardness levels, continue to regularly test and monitor the pool water to ensure the levels remain within the desired range. Test for calcium hardness, pH, alkalinity, and other key water parameters to maintain a balanced and healthy pool environment.

Lowering Calcium Hardness in Gunite Pools

Lowering high calcium hardness levels in a gunite pool can be achieved through several methods. Here are some common approaches to consider:

Partial Water Replacement

Partial water replacement is a technique used to address high calcium hardness levels in pool water. The process involves draining a portion of the pool water, typically around 10-20% of the total volume, in order to remove some of the water with high calcium content. By removing a portion of the water, you effectively reduce the concentration of calcium in the pool.

To begin, you would need to drain the targeted percentage of the pool water. This can be done by using a pool pump or a drain specifically designed for this purpose. It is important to ensure that the drained water is properly disposed of in accordance with local regulations.

Once the desired amount of water has been drained, the next step is to refill the pool with fresh water. It is recommended to use water that has a lower calcium content than the pool water that was drained. This can help dilute the overall calcium hardness levels in the pool.

When refilling the pool, you have the opportunity to choose a water source with a lower calcium content. It is advisable to test the calcium hardness levels of the fresh water before adding it to the pool to ensure that it is indeed lower than the drained water. Testing kits are readily available for this purpose and can provide accurate readings of the water’s calcium hardness.

Complete Water Replacement

Complete water replacement is a process in which the entire pool water is emptied and replaced with fresh water. This procedure is typically performed to address specific issues such as high calcium levels or excessive mineral content in the pool.

To initiate the complete water replacement, the pool is first drained of all its water. This involves removing the existing water through a drainage system or by using pumps. During this step, any debris or sediment that may have accumulated at the bottom of the pool is also eliminated, ensuring a clean starting point for the refilling process.

Once the pool is completely empty, the next step is to refill it with fresh water. However, in the case of addressing high calcium levels, it is crucial to use water that has a lower calcium content than the previous water. This helps to reduce the overall calcium hardness in the pool, which can be beneficial in preventing scaling, damage to pool surfaces, and other related problems.

The source of the freshwater used for the refill can vary. It may come from a municipal water supply, a well, or other water sources. It is important to test the calcium content of the fresh water before initiating the refill to ensure that it has a lower calcium concentration than the previous water.

Sequestering Agents

Sequestering agents, also known as chelating agents or metal sequestrants, play an important role in water treatment, particularly in controlling and preventing scaling issues caused by high levels of calcium hardness. When the calcium hardness in pool water exceeds the recommended levels, it can lead to the formation of scale deposits on various surfaces, such as pool walls, pipes, and equipment.

Sequestering agents work by binding to the excess calcium ions present in the water. These chemicals form stable complexes with the calcium ions, effectively sequestering or capturing them. By doing so, sequestering agents prevent the calcium ions from reacting with other substances in the water and forming scale deposits.

It’s important to note that sequestering agents do not lower the actual calcium hardness levels in the water. Instead, they help manage and control the effects of high calcium hardness by keeping the calcium ions in a soluble and dispersed state. This dispersion prevents the calcium ions from precipitating out of solution and forming scale deposits.


Flocculants are chemical agents that are used in pool maintenance to assist in the removal of small particles suspended in the water. These particles can include calcium particles, among other impurities.

When flocculants are added to the pool water, they work by attracting and binding these small particles together, forming larger clumps or flocs. These flocs are heavier and settle more easily to the bottom of the pool or can be captured by the pool filter.

In the context of calcium hardness, flocculants can be beneficial because they can help bind the calcium particles together, making them larger and more easily removable. By doing so, the flocculants aid in reducing the calcium hardness levels in the pool water.

However, it’s important to note that using flocculants alone is not sufficient to address calcium hardness. Once the flocculation process is complete, proper filtration and backwashing are necessary to remove the flocs and filtered out particles from the pool system. This ensures that the bound calcium particles are effectively eliminated from the pool water.

Combination methods

Combination methods for managing calcium hardness in pool water can be effective in reducing the levels of calcium. One such method involves a combination of partial water replacement and supplementation with soft water.

To implement this method, a portion of the pool water is drained to create space for fresh water. The amount of water drained depends on the current calcium hardness level and the desired reduction. It is important to ensure that the pool water level remains within the recommended range during this process.

Once the partial water replacement is complete, the refilling process begins using soft water. Soft water typically has a lower calcium content compared to regular tap water. This can be achieved by utilizing a water softener or using pre-softened water from an alternative source.

By introducing soft water during the refilling process, the overall calcium hardness level in the pool water is gradually lowered. Soft water contains fewer calcium ions, which helps to dilute the concentration of calcium in the pool.

Combining partial water replacement with the use of soft water can be particularly effective in areas with hard water, where the natural calcium content in the water source is high. By replacing a portion of the water with soft water, the calcium hardness level is effectively reduced, leading to improved water balance and reduced risk of scaling and damage to pool surfaces.

Dry Acid Treatment

Dry acid, or sodium bisulfate, is a powdered substance that is readily available in the market. It is specifically designed for the purpose of adjusting various water parameters in swimming pools, with calcium hardness being one of them. By carefully following the manufacturer’s instructions, pool owners can effectively utilize dry acid to achieve the desired reduction in calcium hardness.

It is crucial to exercise caution and precision when using dry acid to avoid any adverse effects on other water parameters. Overdosing or improper application of dry acid can potentially disrupt the balance of the pool water, impacting factors such as pH, alkalinity, and chemical equilibrium. Therefore, it is essential to carefully measure and add the appropriate amount of dry acid as directed by the manufacturer.

When adding dry acid to the pool water, it is recommended to distribute it evenly across the pool’s surface. This ensures proper dispersion and allows for uniform reduction of calcium hardness. It is advisable to add the dry acid in small increments, allowing time for it to dissolve and mix thoroughly with the pool water before adding more.

How to Balance Hardness Levels in Gunite Pool Naturally?

To balance hardness levels in a gunite pool naturally, there are several approaches you can take. Here are some tips and methods:

  • Monitor and Adjust Calcium Hardness: Regularly test the calcium hardness level in your gunite pool using a pool water testing kit or test strips. The optimal range for calcium hardness is typically between 200 to 400 parts per million (ppm). If the calcium hardness level is too high, it can lead to scaling and other issues, while low levels can cause corrosion. Adjust the calcium hardness level accordingly to maintain it within the recommended range.

  • Dilution with Soft Water: If the calcium hardness level is excessively high, one natural method is to dilute the pool water with soft water. This can be achieved by partially draining the pool and refilling it with water that has lower calcium hardness levels. However, this method should be used with caution, as it can also affect other water parameters, such as pH and total alkalinity. Regular monitoring and adjustment of these parameters are essential when diluting the water.

  • Rainwater Collection: Collecting rainwater and using it to top up or partially refill the pool can help reduce calcium hardness levels. Rainwater is typically soft and has a lower mineral content compared to tap water. However, ensure that the rainwater collection system is clean and free from contaminants before using it in your pool.

  • Natural Filtration: Consider using natural filtration systems, such as zeolite or crushed glass, in your pool’s filtration system. These filtration media have the potential to remove some minerals, including calcium, from the water, helping to balance the hardness levels over time. Consult with a pool professional to determine the suitability and effectiveness of such filtration options for your specific pool.

  • pH and Alkalinity Management: Properly managing pH and total alkalinity levels in your pool can indirectly impact calcium hardness. Imbalanced pH and alkalinity levels can contribute to scaling or corrosion issues. Maintain the pH within the recommended range of 7.4 to 7.6, and total alkalinity within the range of 80 to 120 ppm to help prevent excessive calcium buildup or depletion.

Preventive Measures and Maintenance Tips for Balanced Calcium Hardness

In addition to testing and adjusting calcium hardness levels as needed, there are several preventive measures and maintenance tips that can help pool owners maintain balanced calcium hardness in their gunite pools. Implementing these practices can minimize fluctuations in calcium hardness and promote overall water balance. Here are some preventive measures and maintenance tips to consider:

  • Regular Testing and Monitoring: Regularly test the calcium hardness levels in your pool using a reliable test kit or professional water testing service. Aim to test the water chemistry at least once a month or as recommended by the pool professional. Monitoring calcium hardness levels enables you to identify any imbalances early and take appropriate actions to maintain balance.

  • Maintain Proper Water Balance: Calcium hardness is just one aspect of water balance in a pool. It is important to also monitor and adjust other water parameters, such as pH, total alkalinity, and sanitizer levels. Properly balanced water chemistry helps prevent fluctuations in calcium hardness and ensures overall pool health.

  • Regular Pool Maintenance: Engage in routine pool maintenance activities to keep the pool surfaces clean and minimize the risk of calcium buildup. Regularly brush the pool walls and floor to prevent scale formation. Vacuum the pool to remove any debris or particles that could contribute to water imbalances. Backwash the filter regularly to maintain its efficiency and prevent calcium sediment buildup.

  • Manage Calcium Content in Water Sources: If your pool is regularly filled using tap water, you may want to consider monitoring the calcium content in your water source. High calcium levels in the source water can contribute to increased calcium hardness in the pool. Using a water softener or pre-filtering the water before adding it to the pool can help reduce calcium content and maintain optimal water balance.

  • Temperature Moderation: Extreme water temperatures can affect calcium hardness and other water parameters. Avoid drastic temperature fluctuations in the pool water as they may cause imbalances. Keep the pool water at a moderate and consistent temperature, and monitor calcium hardness levels more closely during periods of extreme heat or rapid temperature changes.

  • Routine Calcium Hardness Management: If your pool consistently experiences high or low calcium hardness levels, consider incorporating specific maintenance routines to manage calcium hardness. This may include periodic partial drain and refills or the use of sequestering agents to control scaling caused by high levels. Consult with a pool professional for tailored recommendations based on your pool’s specific needs.

By following these preventive measures and maintenance tips, you can effectively manage and maintain balanced calcium hardness levels in your gunite pool. Regular testing, proper water balance, routine maintenance, and temperature moderation all contribute to a healthy and enjoyable swimming experience while prolonging the life of your pool surfaces.

How to Remove Calcium Deposits From Gunite Pool Surface?

Removing calcium deposits from the surface of a gunite pool can be a challenging task, but with the right approach, it can be accomplished. Here are some methods to help remove calcium from a gunite pool surface:

Manual Removal

  • Use a stiff-bristled brush or a pumice stone specifically designed for pool surfaces to scrub the affected areas. Apply gentle but firm pressure to remove the calcium buildup. Be cautious not to damage the pool surface while scrubbing.

  • A high-pressure washer can be used to remove stubborn calcium deposits from the pool surface. Adjust the pressure and distance from the surface to avoid damaging the gunite.

Acid Washing

  • Acid washing should only be considered for severe calcium buildup that cannot be removed through manual means. However, acid washing can damage the pool surface and should be approached with caution. It is advisable to seek professional assistance to perform an acid wash properly.

  • Diluted muriatic acid or a specific pool acid wash product can be used. Follow the manufacturer’s instructions and wear protective gear, such as gloves and goggles, to ensure personal safety.

  • Before applying the acid wash solution, wet the pool surface and nearby vegetation with water to prevent damage from the acid.

  • Apply the acid wash solution onto the affected areas using a brush or sprayer, following the manufacturer’s recommendations for dilution and contact time. Let the solution sit for the specified time without letting it dry or exceed the recommended contact duration.

  • Rinse the pool surface thoroughly with water to neutralize and remove the acid. Ensure that all residue is adequately rinsed off before restoring the pool to normal operation.

Professional Cleaning Services

  • If the calcium buildup is extensive and difficult to remove, or if you prefer to leave the task to professionals, consider hiring a professional pool cleaning service. They have the expertise and appropriate equipment to safely and effectively remove calcium from the pool surface without causing damage.

It’s important to note that preventing calcium buildup is key to avoiding the need for extensive cleaning. Maintaining proper water chemistry and balance, including calcium hardness levels, can significantly reduce the likelihood of calcium deposits forming on the pool surface. Regularly brushing, cleaning, and maintaining the pool surfaces can also help prevent the accumulation of calcium and other mineral deposits.

Before attempting any calcium removal methods, it is recommended to consult with a pool professional or expert for guidance tailored to your specific situation. They can provide advice, determine the best course of action, and ensure that the pool surfaces are not damaged during the calcium removal process.


Maintaining proper calcium hardness levels in a gunite pool is essential for the health and longevity of the pool. Adequate calcium hardness helps prevent corrosion, scaling, and other water quality issues that can damage pool surfaces and equipment. By understanding the role of calcium hardness in gunite pools and regularly testing and monitoring the levels, pool owners can ensure a balanced water chemistry and a comfortable swimming environment.

Testing for calcium hardness can be done using various methods such as test kits or electronic testers. It is important to follow the manufacturer’s instructions and guidelines to obtain accurate readings. Regular testing, ideally once a month or after significant water changes, allows pool owners to make necessary adjustments to the calcium hardness levels as needed.

Balancing calcium hardness in a gunite pool involves both increasing and decreasing the levels when necessary. Calcium hardness increasers like calcium chloride can be used to raise the levels, while partial or complete water replacement, flocculants, and dry acid treatments can help lower high calcium hardness levels. Following the manufacturer’s guidelines and taking necessary precautions ensure a safe and effective process.

Implementing preventive measures and maintenance tips, such as regular pool maintenance, managing calcium content in water sources, and maintaining proper water balance, helps to prevent imbalances and promote overall pool health.

By incorporating these practices and staying proactive with calcium hardness management, pool owners can enjoy a well-maintained gunite pool with balanced water chemistry. Regular testing, routine maintenance, and care will contribute to the longevity and enjoyment of the pool, providing a safe and pleasant swimming experience for years to come.

Frequently Asked Questions

1. How do I stabilize the hardness in my pool?

To stabilize the hardness in your pool, it’s important to maintain the calcium hardness level within the recommended range of 200-400 ppm. Regularly test the water using a calcium hardness test kit and make adjustments as needed by adding calcium hardness increaser or using other methods to balance the calcium levels.

2. Will baking soda lower hardness in pool?

Baking soda is primarily used to raise the total alkalinity in pool water, not to lower hardness. It can indirectly impact hardness levels by helping to maintain pH stability, which in turn can affect the precipitation of calcium. However, for significant reduction of hardness, other methods such as dilution or using a calcium hardness reducer are more effective.

3. Does shocking a pool raise calcium hardness?

No, shocking a pool does not directly raise calcium hardness. Shocking refers to adding a high concentration of chlorine to eliminate contaminants. While it may cause a temporary increase in total dissolved solids (TDS), which includes minerals like calcium, it does not specifically target or raise calcium hardness.

4. Can you swim in a pool with high hardness?

Swimming in a pool with high hardness levels is generally safe for swimmers. However, maintaining proper water balance, including calcium hardness, is essential for the longevity and maintenance of the pool and its equipment. High hardness levels may lead to scaling, cloudy water, and potential damage to pool surfaces and equipment.

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Written By Scott Keller

Scott Keller is an experienced pool industry professional with over 20 years of expertise in gunite pool design, construction, and maintenance.

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