How Do I Balance Calcium Hardness in My Pool?

Use a calcium increaser to raise levels or partially drain and refill the pool to lower excessive hardness.

What is Calcium Hardness in Pool Water?

Calcium hardness refers to the amount of dissolved calcium in your pool water. Calcium is a mineral that naturally occurs in many water sources and is an essential part of maintaining water balance. It helps prevent corrosion, protects pool surfaces, and ensures that water is neither too aggressive nor too prone to scaling.

• Ideal Range: The ideal calcium hardness level for pool water is between 200 and 400 ppm (parts per million).

• Too Low: If calcium hardness is too low, it can lead to “soft” water, which is corrosive and can damage pool equipment, plumbing, and surfaces.

• Too High: If the calcium hardness is too high, it can lead to calcium scaling, which can form on pool surfaces, tiles, and inside the filtration system.

Why is Calcium Hardness Important in a Pool?

Calcium hardness affects several aspects of your pool’s operation and water quality. Here’s why it’s essential to maintain balanced calcium levels:

1. Preventing Corrosion of Pool Equipment

Low calcium levels in pool water can lead to corrosion of metal components, including pumps, heaters, ladders, and railings. When the calcium hardness is too low, the water becomes more aggressive and can eat away at the pool’s metal parts.

• What to do: Ensuring proper calcium levels helps protect your pool equipment from costly damage and extends the life of your pool’s infrastructure.

2. Avoiding Calcium Scale Formation

On the flip side, when calcium hardness is too high, it can lead to the formation of calcium scale. This white, chalky substance can build up on tiles, pool surfaces, and even inside the plumbing system.

• What to do: Too much calcium in your pool water can make the water cloudy, clog the filter, and make cleaning the pool more difficult. Scale buildup is also very hard to remove once it has formed.

3. Maintaining Balanced Water Chemistry

Calcium hardness directly affects the overall balance of your pool water. If calcium hardness is off, it can throw off the pH, alkalinity, and other key elements that make up proper pool chemistry.

• What to do: Regularly testing and adjusting calcium hardness helps keep the rest of your pool’s water chemistry in check and ensures a healthy swimming environment.

4. Protecting Pool Surfaces and Finish

Low calcium levels can cause the pool’s surfaces to become rough or even lead to cracks. High calcium levels, on the other hand, lead to the formation of scale on surfaces, which can damage the pool’s finish and make it more difficult to clean.

• What to do: Balanced calcium hardness protects your pool’s finish and ensures that the water remains comfortable for swimmers.

How Do You Test Calcium Hardness in Pool Water?

Before you can adjust the calcium hardness, it’s important to know where your pool stands. Testing the calcium hardness is a simple process, but it requires the right tools and proper technique.

1. Using a Pool Test Kit

A pool test kit is one of the most common and reliable ways to measure calcium hardness. These kits typically include liquid reagents or test strips that react with the water sample to give you a reading.

• What to do: Follow the instructions on the kit carefully. Collect a sample of pool water, add the reagent, and compare the color change to a reference chart to get the calcium hardness level.

2. Using Test Strips

Test strips are an easy and convenient option for measuring calcium hardness. Simply dip the strip into your pool water, and after a few seconds, compare the color change to the reference chart provided with the strips.

• What to do: Test strips offer a quick and simple way to monitor your pool’s calcium hardness. However, they may not always provide the most precise reading compared to a liquid test kit.

3. Pool Store Testing

If you prefer a more accurate result, many pool stores offer free or low-cost water testing services. They can provide you with a detailed analysis of your pool’s water chemistry, including calcium hardness.

• What to do: Bring a water sample to your local pool store, and they’ll provide you with a thorough reading of your calcium levels.

How to Adjust Calcium Hardness in Your Pool

Once you’ve tested the calcium hardness, you may need to adjust it depending on whether it’s too high or too low. Here’s how to make the necessary adjustments:

1. How to Raise Calcium Hardness

If the calcium hardness is too low, you’ll need to raise it to the optimal range (200-400 ppm). The best way to do this is by adding calcium chloride, a chemical that dissolves in water and increases calcium levels.

• What to do:

  1. Test the Water: Determine your current calcium hardness level using a test kit or test strips.

  2. Calculate the Amount Needed: Refer to the manufacturer’s instructions or a pool chemical calculator to determine how much calcium chloride to add based on your pool’s size.

  3. Add Calcium Chloride: Slowly pour the calcium chloride into the pool, preferably near the deep end to allow for even distribution.

  4. Allow for Circulation: Turn on the pool pump and allow the water to circulate for at least 24 hours.

  5. Retest: After circulation, retest the water to ensure that the calcium hardness is within the desired range.

2. How to Lower Calcium Hardness

If the calcium hardness is too high, you may need to lower it to avoid scale buildup. The best method for lowering calcium hardness is to dilute the pool water by draining and refilling part of your pool.

2a. Draining and Refilling

Draining some of the pool water and replacing it with fresh water helps dilute the calcium levels and bring them back into the ideal range.

• What to do:

  1. Drain Some Water: Depending on how high the calcium hardness is, drain around 25-50% of the pool water.

  2. Refill with Fresh Water: Replace the drained water with fresh water that has lower calcium hardness.

  3. Retest: After refilling, retest the calcium hardness levels and adjust as necessary.

2b. Using a Calcium Hardness Reducer

There are specific chemicals available that can help reduce calcium hardness. These products help bind with excess calcium and remove it from the pool.

• What to do: Follow the manufacturer’s instructions for adding the calcium hardness reducer. After adding, run the pool pump and retest the water after 24 hours.

How Often Should You Test and Adjust Calcium Hardness?

Testing and adjusting calcium hardness should be part of your regular pool maintenance routine.

1. Monthly Testing

It’s recommended to test your calcium hardness levels at least once a month during the swimming season. This will help you stay on top of any fluctuations and make adjustments before problems arise.

• What to do: Test the calcium hardness regularly and make adjustments as needed.

2. After Heavy Rain or Pool Refills

If you experience heavy rainfall or need to refill your pool, it’s a good idea to test the calcium hardness again, as these factors can dilute or raise the calcium levels.

• What to do: Test and adjust the calcium hardness after refilling or heavy rain.

3. After Pool Maintenance or Chemical Additions

After any significant pool maintenance or chemical treatments (such as adding algaecide or shock), retest the calcium hardness to ensure it hasn’t been affected.

• What to do: Make sure to check calcium hardness after performing other pool maintenance tasks.

Best Practices for Maintaining Calcium Hardness

To ensure the longevity of your pool and equipment, here are some tips for maintaining balanced calcium hardness in your pool:

1. Maintain Proper Water Chemistry

Proper pH, alkalinity, and calcium hardness are all interdependent. Ensure that your pool water is well-balanced to prevent fluctuations in calcium levels.

• What to do: Test and adjust pH and alkalinity levels regularly to keep calcium hardness stable.

2. Use a Pool Cover

Using a pool cover when the pool is not in use helps reduce evaporation, which can affect calcium levels.

• What to do: Keep your pool covered when it’s not in use, especially during off-seasons.

3. Regular Pool Maintenance

Regular cleaning and maintenance, including checking for leaks, skimming debris, and cleaning the filter, can help keep your calcium levels balanced and reduce the chances of scale buildup.

• What to do: Incorporate calcium hardness checks into your weekly or monthly pool maintenance routine.