How Do You Raise The Hardness In A Swimming Pool

What is hardness in a swimming pool?

Definition of hardness

Hardness refers to the level of calcium and magnesium ions present in the water of a swimming pool. These minerals are naturally occurring and can be found in varying amounts depending on the source water.

Importance of maintaining proper hardness levels

Maintaining proper hardness levels is essential for the overall health and longevity of your swimming pool. When hardness levels are too low or too high, it can lead to various issues that can damage pool equipment and surfaces.

Why is hardness important in a swimming pool?

Effects of low hardness

  1. Corrosion of pool equipment: Low calcium levels can cause corrosion on metal components such as pumps, heaters, and filters.
  2. Etching of pool surfaces: Insufficient calcium can result in etching or pitting on plaster, concrete, or vinyl liner surfaces.

Effects of high hardness

  1. Scale formation on pool surfaces: Excessive calcium levels lead to scale buildup on tile lines, walls, filters, and other areas exposed to water.
  2. Reduced effectiveness of sanitizers: High calcium concentrations interfere with chlorine’s ability to sanitize effectively by creating an environment where algae thrives.

Testing the hardnesss

Importance regular testing

Regularly testing your swimming pools’ hardness ensures you have accurate information about its mineral content so that you can take appropriate actions accordingly.

Methods for testing hardeness

There are several methods available for testing your pools’ hardeness:

  • Test strips provide a quick and convenient way to measure hardeness by simply dipping them into the water.
  • Liquid test kits offer more precise results but require following instructions carefully.
  • Electronic testers use advanced technology for accurate readings but may be pricier than other options.

Adjusting Hardness Levels

When adjusting your pools’ hardeness levels:

Increasing Hardness

To increase hardsess:

1.Adding Calcium Chloride
2.Calculate the Required Amount
3.Distribute Chemical Evenly

Decreasing Hardness

To decrease hardness:

  1. Dilution with Fresh Water
  2. Partial Draining and Refilling
  3. Use of a Water Softener

Maintaining proper hardness levels

Regular testing and monitoring

Regular testing, preferably on a weekly basis, helps you keep track of your pool’s hardeness levels.

Factors affecting hardness levels

Several factors can impact your pool’s hardeness over time:

  • Evaporation: As water evaporates, minerals like calcium and magnesium become more concentrated.
  • Rainwater: When it rains, the water introduces additional minerals into the pool.
  • Chemical treatments: Some chemicals used to balance pH or sanitize may affect hardeness as well.

Common mistakes to avoid

When it comes to maintaining proper hardeness in your swimming pool, there are some common mistakes you should avoid:

  • Overdosing with calcium chloride: Adding too much calcium chloride can lead to excessive scale formation.
  • Neglecting regular testing and maintenance: Not keeping an eye on hardeness levels can result in imbalances that cause damage over time.
  • Ignoring the effects of rainwater and evaporation: These natural processes can significantly impact mineral concentrations in your pool.


Maintaining proper hardness levels is crucial for preserving the integrity of your swimming pools’ equipment and surfaces. Regularly test for hardness using various methods such as test strips or liquid kits. Adjusting hardness involves adding or diluting certain substances depending on whether you need to increase or decrease its level respectively. By paying attention to these factors and avoiding common mistakes mentioned above will ensure optimal conditions for enjoyment while minimizing potential issues related to improper hardness.

FAQ Section

Q: What is an acceptable range for calcium hardness in a swimming pool?

A: The ideal range for calcium-hardness level falls between 200-400 ppm (parts per million). This range ensures that the water is not too soft or too hard, preventing any potential damage to pool surfaces or equipment.

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Q: How can I increase calcium hardness in my swimming pool?

A: To raise calcium hardness levels, you can add calcium chloride dihydrate. Calculate the required amount based on your pool’s volume and distribute it evenly across the water surface.

Q: Can I decrease calcium hardness in my swimming pool?

A: Yes, you can reduce calcium hardness by diluting your pool water with fresh water or partially draining and refilling the pool. Another option is using a water softener if necessary.

Q: How often should I test for hardness in my swimming pool?

A: It is recommended to test for hardness at least once a week to ensure proper maintenance of your swimming pools’ chemical balance and prevent any potential issues arising from imbalances.


Alkalinity: The measure of the water’s ability to resist changes in pH. Adjusting alkalinity levels can help stabilize the pool’s pH.

Pool owners: Individuals who own and maintain a swimming pool.

Soft water: Water with low mineral content, typically measured by low levels of calcium and magnesium.

Muriatic acid: A strong acid used to lower pH and total alkalinity in pool water.

Calcium hardness increaser: A chemical product used to raise the level of calcium hardness in a swimming pool.

Chemistry: The study of how substances interact with each other. In this context, it refers to understanding the chemical composition and reactions that occur in a swimming pool.

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Bucket: A container used for measuring or transferring liquids or chemicals during maintenance tasks.

Alkalinity levels: The measurement of the concentration of alkaline substances (such as bicarbonates) in the pool water. It affects the stability of pH levels.

Soda ash/sodium carbonate/sodium bicarbonate/baking soda: Chemicals commonly used to increase total alkalinity and raise pH levels in a swimming pool.

Hours (in reference to treatment): The amount of time needed for certain treatments or chemicals to take effect before retesting is required

Water hardness/levels of calcium/magnesium salts/magnesium hardness/calcium hypochlorite/water source/water supply/gallons/liters/of water/concentration level/increase/decrease/reduce/treat/enhance/change/stabilize – These terms refer to various aspects related specifically on how calcium hardness is managed, measured, adjusted, or treated within a swimming pool environment according to specific requirements and recommendations based on local conditions & guidelines from professionals such as Pool Chemistry experts/manufacturers/distributors etc.,

Protective gear/personal protective equipment(PPE): Equipment worn by individuals performing maintenance tasks like handling potentially hazardous chemicals. This may include gloves, goggles, masks/respirators, and aprons.

Cloudy water: Water that appears hazy or turbid due to suspended particles or imbalanced chemistry.

Calcium deposits/calcium lumps/calcareous deposits: The accumulation of calcium carbonate on pool surfaces, commonly seen as white scale-like formations.

Pounds of calcium chloride/calcium increaser/calcium hardness increaser products: Measurement units used when adding chemicals like calcium chloride to increase the level of calcium hardness in a swimming pool.

Swimming pool calcium hardness/pool chemistry/water chemistry/magnesium salts/sodium/color/Baking soda/level of minerals/plaster pool/pool pump/powder form/forms/Cost/Undesirable effects/hardness levels/ideal level/chlorine levels/Optimal range/wide range/Maintaining Pool Calcium Hardness/Raising Pool Calcium Hardness – These terms are related to the general understanding and practices involved in maintaining proper levels of calcium hardness in a swimming pool. It includes considerations for different types of pools (e.g., plaster), use of chemicals (e.g., chlorine), recommended ranges, potential issues with high or low levels, and methods for raising or maintaining the desired balance.

Short-term/long-term/immediate/instant/effectiveness/treatment options/measures/remedies/prevention methods/precautions/action plan/resources/advice/articles/research/studies – These terms relate to various strategies, techniques, approaches & suggestions available for effectively managing & addressing concerns associated with maintaining appropriate levels & overall health-related aspects such as long term stability required specifically related to “calcium harness” based challenges within a swimming pool context

Concrete pool walls/concrete surface – Refers to the material used for constructing the inner walls and floor surface area typically made up using concrete mixtures which require special care towards calcification build-up prevention mechanisms

Water temperature/pool chemicals/swimming-pool-water-maintenance tools-Pertain mainly to factors such as temperature, chemical reactions, and use of equipment/tools in swimming pool water maintenance.

Swimming pool water/tap water/municipal water/Hardness levels/ideal level – Relates to the type and quality of water used for filling or refilling a swimming pool. It includes considerations regarding hardness levels based on recommended ranges.

Attention to calcium hardness/calcium carbonate/calcium coating/calcium content/calibration tests/salt chlorinator/deposits/formations/water testing kits/water balancing/dosing instructions/chemical products/pool supplies/pool maintenance aspects/swimming-pool-water-maintenance-customized treatment plan/acidity/stabilization methods/procedures/recommendations/measures-similarly associated with maintaining appropriate calcium harness focusing primarily on additional detailed attention towards proper balance & stability which is considered vital for effective long-term pool health management

Corrosive Water: Refers to the property of the water causing damage or erosion over time. In this context, corrosive waters can lead to damaging effects on plaster surfaces due to imbalanced chemistry.

Clogged filters/filter medium: When debris or contaminants accumulate within a filter system (e.g., cartridge filters), impeding proper flow and filtration efficiency.

Carbonate aka soda/Sodium bicarbonate/Soda ash/Salt level/Major issues/Chemical issues/Expensive issues/Adequate minerals/expensive equipment/balance levels – These terms pertain more broadly to various components and concerns related not only specific application but overall general understanding around key factors affecting comprehensive aspects involved in managing balanced “pool-water-chemistry” efficiently while emphasizing the importance of keeping track elements like salt/minerals balance etc

6-8 hours/Couple hours/Product label instructions/Destruction of metals/Dollars in Pool Supplies/Stability measurements/Pump fires/Form clumps/Rainwater dilution/Large amounts/Budget considerations/Waste disposal costs-Specifically highlighted relating certain activities/information which is typically included within manuals, product labels, & usage instructions often helpful to maintain focus on considering specific time-frames involved in procedures, importance of disposal guidelines for chemical waste and potential implications associated with failing follow them while emphasizing financial aspects and repercussions

Testing kit/additional testing: Tools or equipment used to measure various parameters such as pH levels, alkalinity, calcium hardness, chlorine levels in the pool water. Additional testing may be necessary for troubleshooting or when specialized information is required.

Note: The glossary provided above defines terms specifically related to raising the hardness in a swimming pool. Other terms unrelated to this topic have been omitted from the glossary.

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Mike Hunter

Mike is the owner of the local pool shop. He's been in the business for over 20 years and knows everything there is to know about pools. He's always happy to help his customers with whatever they need, whether it's advice on pool maintenance or choosing the right chemicals. He's also a bit of a pool expert, and is always happy to share his knowledge with anyone who's interested.

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