Calcium Hardness Increaser

Pool Calcium Hardness Increaser - How Does It Work?

One lesser-known aspect of your pool’s water chemistry is calcium hardness. While maintaining ideal levels of calcium in your pool is necessary for a number of reasons, it can be confusing to use a pool hardness increaser for the first time.

In this article, we will discuss what calcium increasers are composed of, what they are used for, as well as how to use them properly.

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What Are Calcium Increasers?

Calcium increasers, sometimes referred to as pool hardness increasers, are products that work to raise the calcium hardness levels of your pool’s water.

Ideal levels of calcium hardness for swimming pools range from 200-400 parts per million (ppm), with the sweet spot being at or slightly below 300ppm.

If you have low levels of calcium hardness in your pool, you will want to use a calcium increaser to raise them. These products contain the compound calcium chloride in varying concentrations.

They are usually quite pure, containing 99%+ calcium chloride.

You should use a calcium increaser in your pool if your calcium hardness is below the recommended range of 200-400 ppm.

Low levels of calcium hardness will lead to corrosive water that can damage your pool surface.

Having low calcium hardness can also cause drops in the total alkalinity and pH levels of your pool, which further exaggerates the corrosive properties of the water.

How To Use A Calcium Hardness Increaser In Your Pool

Most metropolitan water sources in Australia contain low amounts of calcium that tend to fall around 50ppm. If you live in a more rural area and feed your pool with bore water, there is a chance that your source water already contains more calcium than this.

Regardless of where you live, it is common to need to add an initial dose of calcium chloride to your pool after filling it in order to get the calcium hardness within the ideal range of 200-400ppm.

#1 - Gather Supplies

To raise calcium hardness in your pool, you will need a calcium hardness test kit, a calcium hardness increasing product, and a nonmetallic bucket and stirring instrument.

Because this product is available in a granulated form, we also recommend wearing protective eye coverings when handling this product, and that you handle it in an area that is well-ventilated yet protected from the wind.

#2 - Test Your Calcium Hardness Levels

Before you use a calcium hardness increaser in your pool, you should test your pool’s calcium hardness levels. Be aware that some kits measure calcium hardness, while others measure total hardness, which can lead to different results.

If using a liquid testing kit, fill the sample vial up with the appropriate amount of pool water. Then, add the ideal number of drops of the testing agents as is outlined in your test kit’s instructions, and mix these solutions as recommended.

After following your test kit’s instructions for preparing your water sample, you will then compare the colour of your water sample to the chart provided in your testing kit in order to determine your pool’s calcium content. This result may be given in ppm or milligrams per litre (mg/L).

#3 - Calculate An Ideal Dose For Your Pool

After determining your pool’s current calcium hardness levels, calculate the ideal dose of product for your pool. Typically speaking, 500 grams of product is capable of raising calcium hardness by 10ppm in a pool of 50,000 litres.

You can also use our pool calcium hardness calculator to figure out an ideal dose for your pool. To use this calculator, simply enter the volume of your pool in litres and your current calcium hardness levels.

Be aware that some products may contain different ingredients or different concentrations of ingredients. Consult the product packaging if in doubt.

#4 - Mix And Add The Product

Calcium chloride should be premixed before being added to your pool. To do this, fill your nonmetallic bucket up with pool water. After the bucket is full of water, add the calcium chloride you have measured out while stirring the solution gently.

This mixing process will generate heat. This is a normal result of the chemical reactions that are occurring as the product dissolves, but it can be startling as this effect does not often happen when mixing other chemicals.

Once the product is fully dissolved in the bucket of pool water, distribute the solution around your pool while the filter is running. It is important to not pour too much of this solution in one spot as it can damage the lining of your pool in its concentrated form.

If you want to be extra cautious, you can dose half of the mixture, then wait a while before adding the rest to ensure it is circulating effectively. It is not recommended that you pour this solution near any intake valves for your pump and filter system.

#5 - Circulate Water And Retest Levels

After you have gradually added your solution, you will need to continue circulating your water for a minimum of 12 hours to allow the product to dissolve fully.

Once this waiting period is complete, you should then retest your pool’s calcium hardness levels to ensure that they are sitting in the appropriate range.


Calcium hardness is an essential component of your pool’s chemistry. When it is too low, it can lead to corrosion of your pool’s surface. Luckily, it is much easier to raise calcium hardness in your pool than it is to lower it.

Calcium hardness increasers are handy products that allow you to add a precise amount of dissolved calcium to your pool in order to regulate its levels and prevent corrosion.

Do you have any questions about calcium hardness increasers or how to use them? Get in touch with us in the comments section, we’d love to help!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.