Calcium Hardness Increaser

Calcium Hardness Increaser

Increasing calcium hardness levels in your pool and hot tubs is essential to prevent damage to your pool and hot tub surface and equipment. The optimum calcium hardness level is 200-400 ppm.

Unlike baking soda, which does not increase calcium levels, most calcium hardness increasers contain the chemical calcium chloride. They are usually sold in granular form that you can purchase in a pool chemical supplies store.

Why It Is Needed

Maintaining ideal levels of calcium hardness in your pool hot tubs and spa water is an essential aspect of proper water chemistry. Like pH and total alkalinity, calcium content can become a source of problems when it gets out of balance. For instance, when calcium levels get too low, your pool becomes cloudy and corrosive and will cause damage to your pool surfaces and equipment. To prevent this, a pool owner will use a calcium hardness increaser to boost the levels of this mineral. These products are available in a wide variety of forms and are generally composed of the compound calcium chloride.

The best way to determine whether your swimming pool is in need of a calcium hardness increaser is by using a test kit. Most testing kits come with a strip that can be used to measure the level of calcium in your water. Simply remove the strip from the water and compare the color of the strip to the color chart provided with your kit. The results of this will indicate if you need to raise calcium hardness.

You should also note that baking soda, which many novice pool technicians mistakenly believe will raise calcium hardness levels in your water, actually does not do this directly. Instead, it will indirectly affect the total alkalinity and pH levels, which do impact calcium levels. Making your pool water unstable.

When looking for a product to boost your pool water calcium hardness, the most cost-effective option is to use calcium chloride. This is a dry, granulated chemical that can be purchased in large amounts at most swimming pool supply stores. This option will typically cost you around $40 per 15-pound bag.

When you are ready to apply this product to your pool water, be sure to wear pool equipment such as a respirator and safety glasses when handling it. This is because it has an exothermic reaction and generates heat when it reacts with the water. It is also a good idea to test your pool's water before applying it so you know exactly what levels are in the water and how much you need to add. This will help avoid any surprises and save you money in the long run.

How It Works

While it may seem odd, calcium content needs to be actively managed (along with pH and total alkalinity) to keep water in proper chemical balance. Ideal levels are 200-400 parts per million, or ppm. If calcium levels are too low, they can damage your pool potentially causing pool corrosion. Unfortunately, it's not as easy to lower calcium levels as it is to raise them. Most methods require partially draining and refilling the pool, which pumps out the existing calcium-rich water and replaces it with tap water containing very low levels of calcium. This is done until the balanced calcium hardness level is achieved.

This can be expensive, and it's still not guaranteed to get your calcium level back to the desired range. The best way to do this is to use a calcium hardness increaser, which raises calcium levels with granular calcium chloride. These are available from most swimming pool retailers in buckets.

You should test your water before using a calcium hardness increaser. A typical test kit includes a vial of water, a calcium reagent and a hardness indicator. The reagent turns the solution pink, and you add the indicator until the color changes to blue. You then count the number of drops of titrant used to reach the endpoint, and multiply that by 10. The result is your water's calcium hardness. This should indicate that it you need to adjust your calcium hardness levels with your pool water.

To test your pool water, pour some of the water from your pool into the vial and mix well. You should then add the reagent and indicator, and follow the instructions in the kit. Occasionally you may experience a purple endpoint instead of the expected blue. This is most likely caused by interference from metal ions in your water (from algaecides, pipes or the source water) and can be corrected by adding five to six additional drops of the titrant.

To use the calcium hardness increaser, spread it evenly over the surface of your pool and allow it to dissolve while circulating. You shouldn't predissolve it, as this generates heat and can burn your skin. Some people prefer to use a sock or glove when applying it, as this helps avoid burning your hands. Follow the product instructions for dosing, and always retest your water after treatment to ensure that it is within the proper range. After each application you can test your calcium hardness levels.

Safety Measures

While chlorine, pH and total alkalinity may be more commonly known pool chemistry factors, calcium hardness also needs to be actively managed to keep water in proper chemical balance. Keeping calcium hardness levels between 200-400 ppm is important to the health of your pool or spa surface and equipment. If your pool is not properly managed, it will cause corrosion seeking out calcium by dissolving it from surfaces it comes into contact with, such as plaster, concrete, tile grout and metal, causing the formation of scale, and creating corrosive water that destroys metal parts.

As with any chemical addition, it is important to take precautions read the manufacturer's instructions and follow them closely. In general, calcium hardness increasers come in liquid or granule form and are mixed with water to make up the solution before being added to your pool or hot tub. When mixing dry chemicals, it is recommended to use a large nonmetallic bucket filled with water and to add the dry product to the bucket of water rather than throwing it directly into your pool. This is because dry chemicals and salt tend to get very hot when they dissolve, and this can cause burns if not handled correctly.

Once the product is mixed, it can be added to the pool or spa according to manufacturer's directions. The ideal hardness level for your water is determined by comparing the color of a water sample to the chart provided with your test kit. Once the product is added, it is important to turn jets ON and to circulate the water a minimum of 20 minutes. This is important as it will distribute the mixture in the pool.

As with any chemical addition, it is essential to monitor your water daily and to record results in a chemical log book or digital pool system so that you can quickly make necessary adjustments to the pH, chlorine, total alkalinity and calcium hardness. Since the calcium hardness level doesn't fluctuate as much as pH or chlorine, it is easier to manage and maintain with less frequent testing. However, if your water is not properly maintained, even one bad day can result in a lot of damage.


Aside from pH, total alkalinity, and chlorine, calcium hardness is one of the most important factors in swimming pool chemistry. It’s also the most costly water factor to manage because it can easily become unbalanced and cause expensive damage. In addition to affecting the condition of surfaces and equipment, low calcium hardness can also corrode metals in pool or spa plumbing and piping.

When calcium levels are too low, water can be strong and becomes hungry and seeks to “eat” or dissolve anything it can that contains calcium. This can include cement, plaster, plaster surfaces paint, filter and metals in pool and spa plumbing. The end result is brittle, deteriorated surfaces and equipment, which can cost thousands of dollars to repair or replace.

High calcium levels can be equally problematic, particularly if the water is hot. This is because calcium’s solubility inversely proportionates to temperature; as the water heats up, less of the mineral can stay dissolved. Unbalanced calcium levels in a heated pool can lead to scale formation on equipment, surface finishes, and piping. The crusty, grayish white calcium sludge that forms is unsightly, can clog filters and snag bathing suits, and makes it difficult for water to flow through.

The best way to avoid these issues and enjoy your pools is to actively manage calcium levels with a reliable test kit and a quality calcium hardness increaser. These chemicals are inexpensive and easy to use, and they help ensure a proper range for your water’s chemical balance.

While many novice pool technicians assume that a ‘calcium hardness reducer’ will remove calcium from the water, this isn’t possible. These products work by using chemical bonds to bind up the calcium temporarily. When the chemicals break down, the calcium is released back into the water and you’re right back where you started! To properly raise calcium levels, you need to add more of the product. To achieve the recommended calcium level.

By maintaining the ph balance of your pool water. You will get to enjoy the benefits of stain control, scaling, correct total hardness level and avoiding costly repairs and chlorine products.

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