How Do I Raise Calcium Hardness in My Hot Tub?

Use a calcium hardness increaser, which typically contains calcium chloride. Follow the product instructions to bring the hardness level to the recommended range.

What is Calcium Hardness in Hot Tub Water?

Calcium hardness refers to the amount of dissolved calcium minerals in your hot tub water. Calcium is an essential mineral that helps stabilize the water chemistry and prevent the water from becoming too aggressive. The ideal calcium hardness level for hot tubs is typically between 150 and 250 ppm (parts per million). Maintaining the proper level of calcium hardness helps to ensure that your hot tub water remains balanced and safe for both the tub’s components and bathers.

• Too Low Calcium Hardness: If the calcium hardness is too low, the water becomes corrosive, which can cause damage to metal parts like the heater, pump, and jets, as well as pool surfaces.

• Too High Calcium Hardness: If the calcium hardness is too high, it can lead to the formation of calcium scale. This white, chalky substance can coat the inside of the hot tub, including the jets, filter, and heater, reducing their efficiency and damaging the equipment.

Why is Calcium Hardness Important for My Hot Tub?

Calcium hardness plays a critical role in keeping your hot tub water properly balanced. Here are the key reasons why calcium hardness is important:

1. Prevents Corrosion

When the calcium hardness is too low, the water becomes aggressive, meaning it can start to corrode metal parts in your hot tub system. Corrosion can lead to costly repairs or the replacement of equipment.

• What to do: Maintaining the right calcium hardness levels will help prevent corrosion of metal parts and protect your hot tub’s plumbing system.

2. Prevents Scaling

If the calcium hardness is too high, the excess calcium can cause scaling. This results in white, chalky deposits on the tub’s surfaces, filters, and inside the plumbing.

• What to do: Proper calcium levels help prevent scale buildup, which can clog the system, affect water circulation, and lead to maintenance issues.

3. Ensures Optimal Water Clarity

Calcium hardness also affects water clarity. Water that is too soft can cause the water to appear cloudy, while high calcium levels can result in calcium deposits that cloud the water.

• What to do: Balanced calcium levels will ensure your water remains clear and inviting, providing a more enjoyable experience for bathers.

4. Protects Your Hot Tub Equipment

Both low and high calcium levels can damage your hot tub’s equipment. Low calcium levels can corrode the heater and plumbing, while high levels can cause scale buildup that clogs the filter and impedes water flow.

• What to do: Maintaining balanced calcium hardness ensures that your hot tub’s system operates efficiently and extends the life of your equipment.

How to Test Calcium Hardness in Your Hot Tub

Before raising the calcium hardness, you need to test the current levels in your hot tub to determine whether you need to make adjustments. Here’s how you can do that:

1. Using Test Strips

Test strips are a simple and effective way to measure calcium hardness in your hot tub. They are easy to use and provide quick results.

• What to do: Dip the test strip into the hot tub water, wait for a few seconds, and then compare the color change to the reference chart that comes with the strips.

2. Using a Liquid Test Kit

Liquid test kits are more accurate than test strips and allow you to get a precise reading of your calcium hardness.

• What to do: Fill the test vial with a sample of hot tub water, add the provided reagent, and compare the color change to the provided reference chart to determine the calcium hardness.

3. Having Your Water Tested Professionally

If you want a more accurate test, you can take a sample of your hot tub water to a pool store for professional testing.

• What to do: Take a sample of your water to a pool supply store that offers water testing services for an in-depth analysis of your calcium hardness.

How to Raise Calcium Hardness in Your Hot Tub

If you’ve tested your hot tub water and found that the calcium hardness is too low, you can raise it by following these steps:

1. Choose the Right Product to Add Calcium

To raise the calcium hardness, you’ll need to add calcium chloride, a compound that is specifically designed to increase calcium levels in pool and hot tub water.

• What to do: Calcium chloride comes in either granular or liquid form, so choose the form that’s easiest for you to use based on your preferences.

2. Determine the Correct Amount of Calcium Chloride

To raise calcium hardness, you will need to calculate how much calcium chloride to add based on the volume of water in your hot tub and the current calcium hardness level.

• What to do: Refer to the manufacturer’s instructions or use a pool chemical calculator to determine the appropriate amount of calcium chloride to add.

3. Add Calcium Chloride to the Hot Tub

Slowly add the calcium chloride to your hot tub water to prevent clumping or uneven distribution. It’s best to add it gradually and allow the water to circulate as you add it.

• What to do: Pour the calcium chloride in front of the water jets to help it dissolve evenly throughout the water.

4. Allow the Water to Circulate

Turn on the hot tub’s circulation system and allow the water to circulate for at least 24 hours after adding the calcium chloride. This ensures that the calcium is properly dissolved and evenly distributed throughout the water.

• What to do: Run the hot tub pump and jets to aid in the circulation of the calcium chloride.

5. Retest the Calcium Hardness

After 24 hours, test the calcium hardness again to ensure it is within the ideal range (150–250 ppm). If necessary, add more calcium chloride and repeat the process until the desired level is reached.

• What to do: Recheck the water chemistry to make sure the calcium hardness is balanced.

How to Prevent Low Calcium Hardness in Your Hot Tub

To prevent low calcium hardness in the future and ensure your hot tub’s water remains in optimal condition, follow these maintenance tips:

1. Regular Testing

Test your hot tub water at least once a month to check calcium hardness levels and other essential water chemistry parameters.

• What to do: Use test strips or a liquid test kit to regularly monitor calcium hardness.

2. Maintain Proper pH and Alkalinity

The pH and alkalinity levels in your hot tub can impact calcium hardness. Keep the pH between 7.4 and 7.6, and alkalinity between 80–120 ppm to prevent fluctuations in calcium levels.

• What to do: Balance the pH and alkalinity to help stabilize calcium hardness.

3. Drain and Refill Regularly

Over time, dissolved minerals, including calcium, can build up in the hot tub water. Draining and refilling your hot tub every 3-4 months can help prevent high calcium levels and ensure the water remains clean and balanced.

• What to do: Drain and refill your hot tub according to the manufacturer’s recommendations.