How to Increase Calcium Hardness in Pool?

A swimming pool’s water balance also includes pH and total alkalinity, and dissolved calcium is an important measurement. The calcium content of water is usually referred to as its “hardness” – high calcium levels indicate hard water; low calcium levels indicate soft water. Even though magnesium is present, calcium is water’s most important dissolved mineral. Too much calcium dissolved in a pool (hard water) can damage it, but too little calcium dissolved in a pool (soft water) can also harm it.

This article aims to explain How to Increase Calcium Hardness in Pool and to discuss why it’s essential to keep a close eye on this water balance level and what can happen to your pool if you maintain a low calcium hardness level. The following articles provide more information about calcium hardness: Maintaining Pool Calcium Hardness and Testing Pool Calcium Hardness.

You learn how to lower your pool’s calcium hardness level by reading the article: Lowering Pool Calcium Hardness.

Calcium Hardness: What Does It Mean?

Do you know what hard water is? There is a possibility that the municipal water in your area is complex. Your water may even come from a well. You have a high mineral content in your water, including calcium.

It’s good to have calcium. The mineral contributes to the health and strength of bones and teeth. Yeah, that’s true. However, it’s not suitable for your pool and all the expensive equipment you bought to keep it clean.

It is important to monitor and balance the calcium hardness of your pool over time to prevent damage caused by an out-of-whack calcium hardness level.

What is the importance of raising pool calcium hardness?

To balance water, calcium hardness needs to be kept in balance. Alkalinity and pH are the other two. When balancing your pool, you should always ensure that total alkalinity, pH, and calcium hardness are balanced first.

The ideal calcium hardness range for swimming pools is 150-400 ppm (parts per million), so it’s good to try to keep calcium hardness between these limits.

How to Increase Calcium Hardness in Pool?

Soft water (low calcium levels) can cause plaster or concrete pool walls to lose calcium from the pool water and cause the vinyl pool to lose its elasticity. Pool owners must deal with low calcium quickly as it can be very costly.

Calcium deposits in pipes and parts can damage a filtration system when the calcium level is too high. Water will inevitably become harder as it evaporates due to simple evaporation, which is accelerated in very hot, sunny climates.

Fortunately, calcium’s hardness changes quite slowly, so monthly testing and adjustment are sufficient.

1- Test Strip Dip

Test the calcium hardness of water using the Calcium Hardness Test Kit test strips. Submerge the strip in the water at the rear end of the pool and keep it within reach.

2 – Read the Results

Take the strip out of the water. Compare the ribbon colors with the kit’s color chart. This will give you an idea of the water’s hardness level. If the level is less than 200ppm, you need to increase the level. 

3- Measure Calcium Chloride

To raise the hardness level, measure out enough calcium chloride. If you need to raise the level by 10 ppm, use 1 1/4 pounds of product per 10,000 gallons of water. For a 20 ppm increase in hardness, use 2 1/2 pounds of product per 10,000 gallons; for a 50 ppm increase, use 6 1/4 pounds.

4- Mix the Solution

Prepare a bucket of warm water. Do not add water to the compound – only gradual amounts of calcium chloride powder should be added to the water. Dissolve the product in water.

5- Put the solution in the container

Start pouring the mixture into the deep end of the pool. Go around the deep edges slowly and pour the mixture until everything is gone. Open the pool filter and run it for at least 6 hours.

6-Reconfirm the hardness

The next day, test your calcium level again. Assuming the levels are correct, check the chlorine and alkalinity levels and adjust as needed. Returns the pool filter to its normal operating schedule.

Video answer: How to Increase Calcium Hardness in Pool – tutorial

How to reduce the calcium hardness of the pool

If you test the water and find that the calcium levels are too high, you should lower the water.

  1. Drain and replace the water. Test the water supply before changing the water. If you have too much calcium, use a hose filter to avoid minerals. Otherwise, it will be a futile exercise.
  2. Use a pool flocculant. If you can’t or don’t want to drain the water from the pool, try using pool balls to collect excess calcium. Once lumps form, the pool needs to be vacuumed manually to remove it. Important: Be sure to turn off the pump and filter before immersing the flocks in water. If you do not want the filter to contain flocculants, you will need to replace the filter media. To do this, you also need to vacuum and discard. You can’t use the flock if you have a cartridge filter.
  3. Try hydrochloric acid. If drainage and lumps don’t work, hydrochloric acid can be added as a last resort. It does not reduce the water’s calcium hardness but increases the saturation level and helps restore the water’s balance.

Why is calcium hardness so low?

The most common cause of low calcium hardness is the ingress of water that is low in dissolved minerals.

  • Water from rain and snow is naturally soft and does not dissolve calcium or magnesium, so if rain or snow enters the pool, the hardness of the calcium may decrease. Living in areas where heavy rain or melting snow enters the pool can reduce the hardness of calcium.
  • Your local water supply usually has much lower calcium hardness levels than the water in your pool. Urban water systems generally have a calcium hardness of about 40-80 ppm. The added freshwater can gradually reduce calcium hardness levels when added to replace water lost by evaporation, backwashing, and swimmers.

Is baking soda an inexpensive way to increase calcium hardness?

No, baking soda does not affect increasing the hardness of calcium. It only raises the pool’s pH and does not affect the hardness of the water. One of the many myths about pool maintenance!

Adding baking soda after adding calcium chloride can cause damage and excessive turbidity, so it is highly not recommended. In my article, I have provided tips on what to do if you add too many clarifiers.

You can also use the pool if you want the cheapest way to chlorinate your pool.

How dangerous are chemicals?

The contact of baking soda with the skin does not cause any harm, but precautions should be taken. At the very least, you can stay safe with respiratory and eye protection.

Calcium chloride, on the other hand, causes an exothermic reaction when mixed with water. In other words, it gets hot. Therefore, use respiratory and eye protection and always wear gloves to keep your hands safe.


How to Increase Calcium Hardness in Pool? Reading these various steps will give you different ways to know how to increase the hardness of pool water most popularly and quickly.

Maintaining correctly balanced water is one of the hardest parts of owning a pool. Calcium hardness is probably the hardest to keep out of the range. This is further inhibited if there is hard water in the water. However, balancing with the correct information can be challenging because you can overcome these problems and provide a healthy and safe pool.

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