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.

Let’s get into it. 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 pool chemicals.

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 wellbeing.

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 it is important to keep track of the calcium levels in your pool water.

Getting to the Right Calcium Hardness Levels

Here’s a guide on what the ideal calcium hardness levels are and how to get them just right.

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 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 will cause scales of minerals to build around the walls of the pool and equipment. It will also raise the pH level and cause the water to become cloudy. In some cases, high calcium hardness can clog your pool’s filters and stop the water from circulating, allowing more bacteria and algae to form.

How to Lower High Calcium Hardness Levels

If you test your water and find that the calcium hardness is too high, there are a few simple processes that’ll 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 both the filter and the pump before adding the flocculant. If flocculant gets into your filter medium, you will have to 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 is corrosive and can dissolve plaster, concrete, stone tiles, grout, and metal equipment that touches the water. This can result in expensive pool repairs if you don’t balance your water levels.

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.

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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 right 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. If it’s stormed lately in your area and you notice debris in your swimming pool, clean it out.

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

Feel free to reach out to me with any questions!

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