How to Increase Calcium Hardness In a Pool 

The calcium hardness level of your pool is an important chemical to test for and adjust in your water. If your calcium hardness is below the recommended level, the water can become acidic, causing the water to corrode the surfaces and accessories of the pool and may irritate the skin and eyes of swimmers. When the calcium hardness drops to low levels, you will have to increase it.

In this article, I will go over some of the cheapest ways to increase the calcium hardness in your pool. Let’s dive in!

Main Takeaways

• The cheapest way to increase calcium hardness in a pool is to use calcium chloride.
• Before you use calcium chloride to increase the calcium hardness levels, make sure to test and balance the pH, alkalinity, and chlorine.
• Baking soda can indirectly raise calcium hardness levels.
• Other ways to increase calcium hardness levels in a pool include: calcium chloride dihydrate, cal-hypo, and tap water.

Cheapest Way to Increase Calcium Hardness In a Pool

The cheapest way to increase your pool’s calcium hardness level is to use calcium chloride. Calcium chloride is sometimes called calcium hardness increaser and is the most common way to increase your calcium hardness level. This very cost-effective chemical costs around $40 for a 15-pound bucket or $2.5 to $3 per pound.

How to Increase Calcium Levels in a Pool Using Calcium Chloride

Calcium chloride is a straightforward chemical to use. But, as with all pool chemicals, you must make sure you follow the proper instructions when using it. Here’s my handy step-by-step guide to ensure you increase your pool’s calcium levels safely and effectively using calcium chloride.

Step One: Test and Balance the Water

Before you do anything else, your pool water must be balanced. Test the water’s pH, total alkalinity (TA), and chlorine levels, and get them to the ideal levels if they are not already. Your pool water’s pH should be between 7.2 and 7.6, your TA between 80 to 120 ppm, and the chlorine between 1 and 3 ppm.

Here’s the test kit I recommend most to my clients, just in case you don’t already have one.

Taylor High Range Swimming Pool Test Kit

This expansive test kit includes nine tests for most pool chemical measurements you need.

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I may earn a commission if you make a purchase, at zero additional cost to you. This in no way impacts my research process or opinions.

Step Two: Test the Calcium Hardness Level

First, test the calcium hardness level of your pool. Use a test strip or a liquid drop test kit to check your levels. Your pool should ideally have a calcium hardness level between 200 to 400 ppm (parts per million).

If it is too high, check out my article on how to lower calcium hardness levels.

Step Three: Calculate How Much Calcium Chloride You Need

Now that you know your current calcium hardness level, you can calculate how much calcium chloride you need to add to your pool. For every 10 ppm of calcium hardness, you need to increase, that’s 2 ounces of calcium chloride per 1,000 gallons of pool water. Use my calcium hardness calculator to help with the pesky math needed.

Step Four: Prepare the Chemical

Before handling any chemical, you must wear the proper protective gear. Cover your arms and legs and wear goggles, gloves, and closed-toe shoes. Once you are ready, get a 5-gallon bucket and fill it three-fourths of the way up with pool water. Then slowly pour in the calculated amount of calcium chloride.

Here are my top two safety tips when preparing the chemical:

1. Make sure to pour in slowly to avoid splashes.
2. Always pour the calcium chloride into the water and not the other way around.

Here’s my recommended calcium chloride. Most brands call this product “calcium hardness increaser,” “hardness plus,” or something similar. It’s typically all the same. Just check the ingredients list, and it should be exclusively calcium chloride.

Pool Mate Calcium Hardness Increaser

This is my go-to calcium chloride. "Hardness Increaser" is just a fancy name for the same thing.

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Step Five: Add the Calcium Chloride to Your Pool

Add the prepared mixture to your pool. Make sure your pump is turned on, and pour the mixture slowly while walking around the perimeter of the pool.

Step Six: Test Again

After the pool water has turned over at least once (after 6-8 hours), check your calcium hardness levels again. It should be within 200-400 ppm.

What’s the Difference Between Calcium Chloride and Calcium Hardness Increaser?

Calcium chloride is the active ingredient that is present in calcium hardness increasers. So, often, pool owners will interchange the words “calcium chloride” and “calcium hardness increaser.” However, although they often mean the same thing, not all calcium hardness increasers use calcium chloride as an active ingredient.

Calcium chloride dihydrate is another common active ingredient found in calcium hardness increasers. While calcium chloride is sold in granular form, calcium chloride dihydrate is typically sold in powder form.

The other difference between calcium chloride and calcium hardness increaser is that calcium chloride tends to be cheaper. While these two products are often technically the same, calcium hardness increaser is marketed differently and more specifically to pools, so the packaging is more expensive. So, when looking for the cheapest way to increase calcium hardness in your pool, look specifically for calcium chloride.

Does Baking Soda Increase Calcium Hardness?

The main use of baking soda in a pool is to increase the pH and total alkalinity levels. Baking soda does not directly increase or impact calcium hardness levels.

However, since this chemical raises the pH of the pool, this can lead to calcium build-up. In other words, by adding baking soda, you can indirectly increase the calcium hardness levels. Despite this, baking soda shouldn’t be your main weapon of choice when tackling too low calcium hardness levels.

That said, as baking soda can indirectly affect calcium hardness levels, you should always balance the water’s pH and alkalinity first before you test and increase the calcium hardness levels.

Other Methods to Increase Calcium Hardness

Besides calcium chloride and baking soda, there are other methods to increase the calcium hardness levels of your pool.

Calcium Chloride Dihydrate

Calcium chloride dihydrate is another active ingredient found in calcium hardness increasers. This type of calcium increaser is generally sold in powder form. The main difference between calcium chloride and calcium chloride dihydrate is that the latter has water molecules.

Calcium Hypochlorite

Another common pool chemical used by pool owners is pool shock, and of the many types of pool shock one can choose from, a popular one is calcium hypochlorite, also known as cal-hypo. As evidenced by its name, cal-hypo contains calcium and is actually a common cause of too much calcium in the water.

So, if you need to increase calcium hardness but you also need to shock the pool, you can kill two birds with one stone by using this chemical to sanitize your pool while also increasing the hardness of your pool water.

Tap Water

In some cases, your local water supply may have a relatively high percentage of calcium hardness already in the water. If this is the case, to raise the calcium hardness level, you can simply do a partial drain of your pool water and fill it up again using a garden hose. Keep in mind that this method depends on your local water supply, so make sure to ask your local municipality about the mineral content of your local water.

Questions? Drop me a line! Always happy to help. And if you’re curious, head to my central article on calcium hardness in your pool for more information on the topic.