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Balancing Pool Calcium Hardness – Complete Guide

April 16, 2024

Knowing the levels of calcium and magnesium in your pool is essential. For example, high calcium can lead to cloudy water and scale build-up whereas low levels can be corrosive.

In this article, we’ll be going over how to check your calcium hardness, why it matters, and the steps for maintaining ideal levels. So be sure to keep reading!

Determining Calcium Hardness in Your Pool

Calcium hardness refers to the amount of calcium ions present in the pool water.

You might ask, why does this matter? The answer is, calcium plays a vital role in your pool’s water chemistry; it influences the balance and health of your pool water, and can contribute to a better swimming experience.

Too much or too little of this mineral can cause problems. High calcium hardness levels can lead to cloudiness in the water and a rough, scaling texture on pool surfaces.

On the other hand, when calcium hardness drops below the ideal range, water becomes corrosive, leading to erosion of the tile grout and other pool components. That’s why it’s so important to maintain proper levels of calcium hardness.

Understanding Calcium Levels

understanding calcium levelsThe ideal calcium hardness range for swimming pools is 150-400 ppm. This is the industry standard range, although spas tend to have a slightly lower range of 150-250 ppm.

Maintaining your pool within these ranges is crucial for proper pool equipment function and water quality.

Consequences of High Calcium

Excess calcium can cause a number of issues including cloudy swimming pool water and a rough, scaling texture on your pool surfaces, the latter of which can affect your pool heaters.

In vinyl and fiberglass pools, excessive calcium hardness can also cause a flaky crust to develop, one that can cause itchy skin.

Risks of Low Calcium Hardness

Low calcium levels also pose threats. When calcium hardness drops below 150 ppm, water becomes corrosive. Over time, this can lead to the erosion of tile grout, delamination of plaster surfaces, and corrosion of metal pool components.

Testing and Adjusting Calcium Hardness

testing and adjusting calcium hardnessPool owners can measure calcium levels using test kits or test strips. Consistent testing is key to sustaining your pool water’s balance.

As a general rule of thumb, you want to test for calcium hardness once a month, or once every two weeks, if you live in an area with hard water.

How to Test for Calcium Hardness

When it comes to testing for calcium hardness, a drop-count titration test is recommended over test strips. This is because it measures in specific 10 ppm increments and distinguishes calcium hardness from total hardness.

To conduct a drop-count test:

  1. Add the buffer and indicator reagents to a water sample
  2. Swirl the mixture
  3. Count the drops until a color change from red to blue signifies the calcium level

The calcium carbonate level in parts per million (ppm) is then determined by multiplying the number of drops used by the equivalence factor provided in the test’s instructions.

Interpreting Your Test Results

To interpret the results from the drop test, you’ll need to be familiar with the Langelier Saturation Index (LSI). Put simply, it assesses the potential of your water to be corrosive or scale-forming based on your calcium hardness test results.

A zero SI value means the water is properly balanced, with the correct calcium hardness, pH, and total alkalinity while an SI value above +0.5 indicates scaling may be an issue.

An SI value below -0.3, on the other hand, signals corrosive water, which can damage plaster, concrete, grout, and metal surfaces within the pool environment.

Strategies to Lower Calcium Hardness

Lowering calcium hardness can be done by partially draining the pool and replacing it with fresh tap water. However, before you replace pool water, you want to make sure the tap water has lower calcium levels.

Alternatively, you can introduce chemical solutions such as sequestering agents to the pool.

Diluting the Pool Water

lower calcium hardnessDraining a portion of your pool water and refilling it with lower calcium content water is an effective way to reduce high calcium hardness levels.

You can reduce the amount of calcium by replacing as little as 30-40 centimeters of water from the swimming pool. After diluting, adjust your pool water’s calcium hardness level so that it’s between 200-400 ppm – that will help prevent calcium from building up.

The Role of Chemical Compounds

Sequestering agents can be used to manage calcium levels in pools. Not only that but they can also help prevent scale formation.

Calcium hardness reducers are also effective but their effects are only temporary as they will only bind with calcium for 4-6 weeks before releasing it back into the water. On the other hand, using a calcium hardness increaser can help maintain the desired levels of calcium hardness in the water.

Certain products, like SC-1000 chelant, can also be added during the calcium dissolving process to ensure the calcium stays in solution and reduces the risk of cloudiness in pool water.

Boosting Low Calcium Hardness

On the other hand, if your calcium levels are too low, you’ll need to raise them to prevent corrosion and damage to your pool.

Adding calcium chloride is the easiest way to increase calcium hardness in pool water. In terms of how much calcium to add, you want to follow the manufacturer’s instructions regarding dosing.

When and How to Add Calcium Chloride

When handling the compound, it is necessary to:

  • Wear safety gear such as glasses and rubber gloves due to the heat generated when it is dissolved in water
  • Pre-dissolve the calcium chloride in a bucket of water before adding it to the pool, with no more than 15 pounds per bucket
  • If the dose exceeds 15 pounds, divide it and add in stages

After dissolving and the solution begins to clear, pour the calcium chloride evenly around the perimeter of the pool to ensure proper distribution.

Ensuring Proper Dissolution

boosing low calcium hardnessLimit the amount of calcium chloride to 10 pounds per bucket and stir continuously until it is fully dissolved to prevent clumping or settling.

If excessive heat is generated during the dissolving process, allow the solution to cool down before adding it to the pool.

Pour the well-dissolved and cooled calcium chloride solution into the pool water afterward in front of a return jet or while walking around the pool to ensure rapid heat dispersion and even distribution.

Maintaining Ideal Calcium Hardness

For a concrete or plaster pool, the recommended calcium hardness range is between 200-275 ppm.

Keeping the pool’s calcium hardness levels within these levels will help prevent:

  • calcium deposits
  • cloudy water
  • scaling on pool surfaces
  • clogged filters

Balancing pH and Alkalinity

In addition to calcium hardness, pH and alkalinity levels also play a crucial role in maintaining balanced pool water chemistry.

For alkalinity levels, you can use muriatic acid to lower it or sodium bicarbonate to raise it.

If the pH of pool water falls below 7.2, soda ash can be used to increase it.

Preventing Calcium Buildup and Deposits

Here are some tips to prevent calcium from building up in your pool:

  • Maintain the pH balance of pool water between 7.4 and 7.6
  • Regularly clean the pool tiles and floor on a weekly or bi-weekly basis
  • Ensure regular cleaning of the pool filter monthly

Using a calcium prohibitor or blocker can also help protect the pool tiles and prevent calcium deposits. An automatic pool cover can also be used to minimize evaporation, which will rduce the concentration of calcium in the water.

Routine Cleaning Techniques

routine cleaning techniquesCalcium deposits can be scrubbed off the pool’s surface using a brush with stiff bristles. Cleaning the pool tiles with a wet pumice stone will also remove calcium without damaging the tiles.

For tougher calcium carbonate deposits, you can use a stain eraser, scale remover, or pumice stone.

Addressing Pool Types and Systems

Different pool types and systems require different considerations when it comes to calcium hardness.

Fiberglass and vinyl liner pools, for instance, have their specific ideal calcium hardness range. The same goes for MagnaPool systems, which have unique calcium hardness requirements that require tailored maintenance.

Fiberglass and Vinyl Liner Pools

Aim for a calcium range of 175-225 ppm if you have a vinyl or fiberglass liner. If necessary, refer to the manufacturer’s guidelines for the suggested calcium levels, as pool shops may offer incorrect advice for calcium levels in fiberglass pools, which often differ from concrete pools.

We also recommend brushing the liners regularly with a soft-bristle brush or sponge to prevent the accumulation of dirt, debris, and undissolved chemicals.

Special Considerations for MagnaPools

In MagnaPool systems, 70% of the total hardness reading is comprised of magnesium salts.

MagnaPool systems are designed to operate with a ‘total hardness’ level of around 800 ppm, which is significantly higher than the 200-300 ppm that is typical for salt pools.

Understanding Pool Calcium Hardness

Managing pool calcium hardness is a crucial aspect of pool maintenance. Whether your calcium hardness levels are too high or too low, there are strategies you can implement to bring them back to the optimal range.

More specifically, regular testing and proper interpretation of results are key. Also, remember that different pool types and systems have different requirements – so be sure to keep that in mind when maintaining your pool.

Key Takeaways

  • Ideal calcium hardness levels range from 150-400 ppm, with low levels causing corrosion and high levels leading to scaling and cloudiness
  • Testing for calcium hardness should be done monthly or more frequently in hard water conditions
  • Maintaining ideal calcium hardness involves regular monitoring and adjustments—using calcium chloride to raise levels and dilution or sequestering agents to lower them

Maintaining the Proper Calcium Levels – Frequently Asked Questions

What should I do if my calcium levels are too high?

To fix the calcium hardness in your pool, you’ll need to lower the level by pumping out a small amount of existing pool water and refilling it with tap water with low calcium levels.

What is the ideal calcium hardness in a pool?

The ideal calcium hardness for a pool is between 200–400 ppm. Keeping it within this range is important for maintaining proper chemical balance in the pool water.

Does baking soda raise calcium hardness?

No, baking soda does not raise calcium hardness. It works with the pH balance of the water but can cause cloudiness if added around the same time as calcium carbonate.

Will shocking the pool increase the calcium hardness levels?

Yes, pool shock will slightly raise the calcium hardness levels, so it’s important to adjust the pH while using it to maintain balance.

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John Harrington

John Harrington, with over 20 years of experience in pool and spa maintenance, generously shares his expertise on the ACTIVE blog. His in-depth knowledge and practical advice provide invaluable guidance for maintaining pristine pools and hot tubs. John's insights help enthusiasts and homeowners ensure their aquatic havens are always in top condition.

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