How to Fix Low Calcium Hardness in Your Pool

Add a calcium hardness increaser to bring levels to the recommended range of 200-400 ppm.

What is Calcium Hardness and Why Does It Matter?

Calcium hardness refers to the amount of dissolved calcium in your pool water. It is an essential part of pool chemistry, and it directly impacts the health of your pool's surfaces and equipment. Proper calcium hardness helps to:

• Prevent plaster damage: Low calcium hardness can cause plaster to become rough and deteriorate, leading to the need for costly repairs.

• Protect pool equipment: Low calcium levels can cause corrosion of metal pool parts, such as ladders, heaters, and pumps.

• Maintain water balance: Calcium hardness plays a key role in maintaining the overall water balance, including pH and alkalinity.

The ideal calcium hardness level for most pools is between 200 and 400 ppm (parts per million). When calcium hardness is below this range, it can create issues that require attention.

Causes of Low Calcium Hardness in Pools

There are several reasons why calcium hardness levels in your pool might be too low:

• Frequent water dilution: If you're constantly adding fresh water to your pool due to evaporation or backwashing, this can dilute the calcium levels.

• Use of soft water: Some areas have soft water that naturally lacks calcium. Filling your pool with soft water can lead to low calcium hardness.

• Rainwater: Heavy rainfall can dilute the calcium hardness in your pool, especially if it’s diluted with soft rainwater.

• Pool cleaning products: Some pool cleaning products can lower calcium hardness over time, especially those containing acids or other chemical additives.

By understanding the causes of low calcium hardness, you can take steps to prevent it from happening in the future.

How to Test Calcium Hardness in Your Pool

Before you fix low calcium hardness, it's essential to test your pool water to determine the exact calcium levels. Here's how you can test for calcium hardness:

1. Use a Pool Test Kit

To test calcium hardness, you can use a pool test kit that specifically measures this parameter. You can either use a liquid test kit or test strips designed for calcium hardness testing.

• Test strips: Test strips are easy to use and provide a quick reading. Simply dip the strip into the pool water and compare the color on the strip with the chart provided.

• Liquid test kits: Liquid kits are more accurate and typically offer a more detailed analysis of your pool's water chemistry.

2. Test Multiple Areas of the Pool

Test the water in multiple areas of the pool to ensure an accurate reading. Pool chemistry can vary slightly in different parts of the pool, especially if the circulation is uneven.

3. Understand the Ideal Calcium Hardness Range

The ideal calcium hardness level is between 200 and 400 ppm. If your calcium hardness level is below this range, your pool water may be too soft, which can lead to issues such as etching and corrosion.

How to Increase Calcium Hardness in Your Pool

Once you’ve confirmed that your pool’s calcium hardness is low, it's time to take action. Here’s how you can increase calcium hardness in your pool:

1. Add Calcium Chloride

The most common and effective way to raise calcium hardness in a pool is by adding calcium chloride. This chemical will increase the calcium levels in the water, restoring the proper hardness.

• Choose the right calcium chloride product: There are two types of calcium chloride products available—dihydrate and anhydrous. The dihydrate form is most commonly used in pools.

• Calculate the amount needed: You will need to add approximately 1.5 pounds of calcium chloride for every 10,000 gallons of water to raise the calcium hardness by 10 ppm.

• Add the calcium chloride: Dissolve the calcium chloride in a bucket of pool water and slowly pour it around the pool’s perimeter, avoiding the skimmer area.

Tip: Always follow the manufacturer’s instructions when adding chemicals to your pool.

2. Retest the Water After a Few Hours

After adding calcium chloride, run the pool pump for at least 4 to 6 hours to allow the chemical to disperse evenly throughout the pool. Afterward, retest the calcium hardness to ensure it has reached the desired level.

• Adjust as necessary: If the calcium hardness is still too low, add more calcium chloride, but be sure to retest frequently to avoid overshooting the ideal range.

3. Avoid Over-Correction

It’s important to avoid adding too much calcium chloride at once, as it can lead to a rapid increase in calcium hardness, causing scaling and cloudy water.

• Add in small doses: Increase calcium hardness gradually, adding the chemical in small doses over several days.

• Wait for proper circulation: Ensure that the pool’s filtration system is running to distribute the calcium chloride evenly throughout the pool.

4. Prevent Future Low Calcium Hardness

Once you’ve corrected low calcium hardness in your pool, it’s important to take steps to prevent it from happening again.

• Test your pool water regularly: Check calcium hardness at least once a month to monitor fluctuations and address any issues before they become major problems.

• Use calcium-rich water: If possible, fill your pool with calcium-rich water. Avoid using soft water or water with a low mineral content, as this can lead to low calcium levels.

• Use a pool cover: Covering your pool during periods of heavy rain can prevent rainwater from diluting the calcium levels in your pool.