How to Balance and Maintain the Calcium Hardness Level in Your Pool

Getting your pool chemicals just right is a science. It’s your best defense against cloudy or dirty water, but it takes practice to perfect. The main levels to keep an eye on are: pH, chlorine, and calcium hardness. Today, I’m going to dive into calcium hardness.

Below, you’ll learn about what calcium hardness is, why maintaining it is vital to the quality of your swimming pool, and how to optimize your levels. For more on water chemistry, make sure to read my complete guide on essential pool chemicals.

Main Takeaways

  • Your plaster or concrete pool should have a calcium hardness of 200-275 ppm, and your fiberglass or vinyl pool should be at 175-225ppm.
  • Test your calcium levels every 2-3 weeks, but also when you drain your pool or add new water or chemicals.
  • To lower calcium hardness levels, drain and replace the water, use flocculant, or use muriatic acid.
  • To raise calcium hardness levels, use a calcium hardness increaser.

What Is Calcium Hardness?

Water described as ‘hard’ usually has a high mineral content (generally calcium or magnesium).

An easy way to tell if your water is hard or soft is to feel the water with your hands. If there is a particularly slimy feeling, it is probably hard water.

Usually, hard pool water looks cloudy or murky. There might also be excess calcium sediment on the surface of the water. This calcium scale can wreak havoc on your swimming pool by decreasing the water circulation through fittings, pipes, and valves and clogging the filters in your pool. If you have a heater in your swimming pool, that will most likely won’t be as efficient. The water pump will have to work twice as hard, too.

If you are experiencing some of these issues and you’ve already tried shocking your pool a few times, chances are, your water is too hard. Getting this under control is very important for your pool’s health.

Why Is Maintaining Calcium Hardness Important?

When calcium builds up in your water, the excess sediment can damage your pool walls and even your equipment. This is why keeping track of the calcium levels in your pool water is important.

Getting to the Right Calcium Hardness Levels

Here’s a guide on the ideal calcium hardness levels and how to get them just right. You can use my calcium hardness calculator to figure out how much calcium hardness increaser to add or pool water to replace.

What’s the Right Level of Calcium Hardness for Your Pool?

There are a few factors that will determine the optimal calcium hardness level, such as the type of pool you have. If your pool is plaster or concrete, you need to aim to keep your calcium hardness at around 200-275 ppm (parts per million). If it’s fiberglass or vinyl, it needs to be at 175-225 ppm. There is a happy medium, so you won’t want the water to be too soft or too hard.

How to Test Your Calcium Hardness Levels

You should test your calcium hardness levels every 2-3 weeks. The most efficient testing method is a liquid drop test because it will give you the most accurate reading. You can also use testing strips, but they will provide a more approximate reading. For more information on using a testing kit, check out my guide for testing pool water.

Effects of High Calcium Hardness on a Pool

High calcium content in your pool water can cause the following:

  • Damage to your pool walls and equipment
  • Scales of minerals built around the pool walls and equipment
  • Rough pool surface
  • High pH level
  • Cloudy water
  • Clogged filters

How to Lower High Calcium Hardness Levels

If you test your water and find that the calcium hardness is too high, a few simple processes will help you get your pool back in shape.

Replace Some of the Water

The first option is to drain some pool water and replace it with fresh water. Make sure to test the water before and after refilling the pool to ensure you have calculated correctly. However, if the tap water in your region is high in calcium, this may not be a viable option.

Use Pool Flocculant

Flocculant is a chemical that will cause the excess calcium to clump together. When these clumps form, they sink to the bottom of the pool, and you can then use your vacuum to remove them.

Remember to turn off the filter and the pump before adding the flocculant. If flocculant gets into your filter medium, you must replace it. Don’t use flocculant if your pool uses a cartridge filter.

Use Muriatic Acid

Try adding some muriatic acid as a last resort. Though this chemical doesn’t lower the calcium hardness in your pool, it does increase the level of saturation, which can balance out your pool water.

Effects of Low Calcium Hardness on a Pool

If your water has low calcium hardness, it is classified as ‘soft’ water. Soft water can lead to the following issues, all of which can result in expensive pool repairs:

  • Corrosion of metal equipment
  • Dissolving of plaster, concrete, stone tiles, and grout
  • Etching of pool surfaces, including pool decking

How to Raise Low Calcium Hardness Levels

The good news is that increasing the calcium hardness in your pool is a lot easier than decreasing it. You can purchase a calcium hardness increaser (like calcium chloride) that will raise your levels when added to your water. Calculating the volume of your pool will help you work out how much of the product to purchase.

You’ll often see this product labeled as “calcium hardness increaser” or “hardness plus,” like Leslie’s pool supply store does in the photo I took below.

Get My Free Pool Care Checklist

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Tips for Maintaining Your Calcium Hardness Levels in the Right Range

Although calcium hardness can be an easy fix, it’s a pain when your pool water levels aren’t balanced properly. Ideally, your calcium hardness levels should be in the correct range at all times.

Here are my best tips for doing this:

1. Keep Your Water Levels Balanced

The easiest way to maintain your calcium hardness levels is to check your pool chemistry frequently. Also, keep an eye out for any changes, especially regarding calcium hardness.

2. Face Any Potential Problems Head-On

You should address any issues as soon as you notice them. For example, don’t wait until your water is too hard. If you see the level increasing, take action immediately.

3. Test Your Water Regularly

Ideally, you should be testing your pool water every week, especially if your water source is hard. You should also check the calcium hardness every time you drain the pool and add new water or chemicals. If you’ve had torrential rain recently, it’s also a good idea to test. The best test kits are usually liquid kits, but test strips work too. Just make sure your test kit includes a test for calcium hardness.

4. Keep Your Pool Clean

Last but certainly not least, keep your pool clean. Keeping your pool clean is a surefire way of staying on top of your pool water’s chemistry levels. Clean it out if it’s stormed lately in your area and you notice debris in your swimming pool.

As long as you’re observant about your chemical levels (particularly calcium hardness, total alkalinity levels, pH, and chlorine levels), you should have no problem.

Frequently Asked Questions

How do you fix calcium hardness in a pool?

Calcium hardness should be between 200-275 ppm for a plaster or concrete pool or 175-225 ppm if you have a fiberglass or vinyl pool. If your calcium hardness levels are too high, drain the pool and replace the water, use a flocculant, or use muriatic acid. Conversely, if your levels are too low, use a calcium hardness increaser.

What causes excess calcium in a pool?

There are many reasons your calcium hardness levels may be out of wack, including hard tap water, high pH, evaporation, lack of water circulation, and fluctuating temperatures.

How do you remove calcium buildup and scaling in a swimming pool?

To remove calcium scale deposits, first, lower the calcium hardness level, get the alkalinity back to 80-120 ppm, check the pH level, and finally, use a scale eraser and scale remover to scrub away the scale.

Feel free to reach out to me with any questions!

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