A Complete Guide to Calcium Hardness in Pool Water

Want to make sure your swimming pool is healthy? Learn about calcium hardness in pool water here. Learn how to test your water and how to treat it if your calcium levels are too high.

You are probably wondering, what is calcium hardness? Calcium hardness levels in a pool are among the most important aspects of maintaining a healthy swimming environment.

A high level of calcium in the water will keep it from staining and reduce chloramines. Conversely, too little calcium and your pipes will become porous over time and corrode.

Porous Pipes

To avoid the issues that come with either too much or too little calcium in your pool, be sure to maintain proper levels through regular chlorine treatments and regular shock treatment as needed. 

Read below to find out why calcium hardness is necessary to your pool and find answers to some of the commonly asked questions about calcium hardness.

What is Calcium Hardness in Pool?

Calcium is a mineral that is commonly added to the pool water. It is important because it prevents the formation of hard water deposits and calcium staining, which can be an unsightly aspect of pool maintenance.

Some pools contain a certain level of calcium hardness at the time they are installed. However, as more people swim in them, problems like corrosion can arise due to water containing too much or too little calcium hardness. The amount of calcium in your pool measures how easily this happens, for example:

  • A balanced level of 180-220 ppm will prevent staining and prevent any corrosion from occurring;
  • A higher level than 220 ppm causes dangerous deposits to form on surfaces.
  • A level below 180 ppm can ruin the pools alkalinity levels.

What Causes Excess Levels of Pool Calcium?

Pool calcium can result from the following activities:

  • A pool owner adding too much Calcium Chloride (CaCl2) or Calcium Hypochlorite (CaOCl2) to your pool.
  • The use of an acid cleaner like sodium chloride, which uses Ca(OH) as a reagent and would generate excess calcium hardness.
  • Using chlorine tablets, shock treatment or water conditioners with high levels of calcium.

Causes of Insufficient Level of Calcium in Pool Water

Heavy Raining on Pool

The following can cause low calcium hardness levels:

  • Rain or other high levels of water run-off sends calcium, along with many other minerals, into the storm drain before your pool can use it. 
  • Overuse of a product containing hydrogen peroxides, such as chlorine tablets or shock treatment.
  • Algae can alter calcium hardness levels.
  • Very high levels of metals such as iron or lead.

Use Calcium Moderately

Yes, using calcium can be a pain in the you know what, so your first instinct is to just skip it completely. However, that will be a huge mistake. While excessive calcium levels might result in murky water and scale, low calcium levels are no better.

Here's why: Water is naturally balanced, so without enough calcium, it will balance itself out by getting calcium from, say, your pools metal fittings and heat exchangers, which eventually cause corrosion that destroys fittings and results in pinhole leaks or draw calcium from your plaster pool walls!

In other words, when it comes to managing the pool’s calcium hardness levels, the "Goldilocks" rule of thumb is best: Not too much, not too little - you want it to be just right.

What’s the Optimal Calcium Content?

Water should have a calcium level of 100-400 parts per million. Less than that will cause corrosion and more will cause murky water.

How to Increase Calcium Hardness Levels in a Pool?

If the calcium levels in your swimming pool aren’t high enough, you can easily increase the levels by adding a pool water hardness increaser. You can purchase a bucket of granular calcium hardness increaser at any swimming pool shop.

How to Lower Calcium Hardness Levels in a Pool?

A sequestering agent or a chemical treatment combats the effects of excessive metal and calcium content in swimming pool water, and pool owners use this to deal with too much calcium buildup in a pool.

If your pool often suffers from excessive calcium levels, or if you reside in an area where hard water is a problem, you should include a sequestering agent in your pool care & maintenance. 

Of course, suppose you’re quite unsure on how to deal with a swimming pool issue yourself – from calcium issues to routine maintenance – your local pool specialist is an excellent source. They can point you to the best way of maintaining your pool and prevent more problems from occurring.

Calcium Hardness FAQS

  • How to measure calcium hardness in the swimming pool safely? You can measure calcium hardness in most pool testing kits. If you’re new to balancing out a pool’s water, test strips are an easy way to go about it.
  • How to get rid of calcium buildup from a pool? Cleaning and de-scaling will help to remove the calcium buildup in a pool. If you haven’t tried using pumice stones, now’s the time to try it. It works wonders for plaster swimming pool surfaces. For tile style pool, however, you should use something less abrasive. For example, you can try vinegar and a scrub brush. 
  • What is total hardness of pool water? Total hardness is the total measurement of magnesium hardness and calcium hardness.
  • Is calcium hardness the same as total hardness? Calcium hardness is the measure of dissolved chlorine in the pool water, and total hardness is the total measurement of calcium and magnesium in the pool water.

Calcium hardness is one of the most important aspects you should take into consideration when maintaining your swimming pool. Hopefully, this short guide has helped you to overcome some of the most important questions about Calcium usage in your swimming pool.

You can find articles about pools on our website. Here are a few tips to help you maintain and clean your pool. Have fun in a clean, safe pool with your family!

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About the author

Brian Anderson

The rather dry pool world out there is in need of some passion to make it shine. With the help of my son Ruben and his wife Maria our mission is to help you create the favorite spot of your house - your pool.

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