Just when you get the alkalinity, pH, and chlorine levels perfect, something sneaks up on you from behind, and throws your pool into chaos—calcium hardness. Should there even be calcium in your pool? How did it get there? How much is too much? Is it possible for there to be too little?
All good questions. And it’s your lucky day, because we’ve got all the answers. Learning how to manage and control the calcium level in your pool is a big step toward keeping it clean, clear, and swimmable all season long.
What Is Calcium Hardness?
You’ve heard of hard water, right? You may live in an area where the municipal water is hard. Or you may even get your water from a well. Either way, it means your water supply has a high level of minerals, including calcium.
But wait, calcium’s a good thing, isn’t it? It makes strong, healthy bones and teeth. Sure, that’s true. But it’s not so good for your pool and all the expensive equipment you bought to keep it clean and healthy.
Over time, an out-of-whack calcium hardness level can do some real damage, which is why it’s so important to monitor and balance the calcium hardness in your pool.
What Is the Correct Calcium Hardness Level?
Here’s your favorite answer: It depends. But what it depends on isn’t that difficult.
If your pool has a vinyl or fiberglass liner, the calcium hardness level should be between 175 parts per million (ppm) and 225 ppm.
If you have a concrete or plaster pool, keep the level between 200 ppm and 275 ppm.
See? Easy.
The key is keeping it balanced. You don’t want your pool water to be too hard or too soft. Either way, you’re in trouble.
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Get Instant AccessWhat If the Water Is Too Hard?
If the calcium hardness level in your pool gets too high, the water will be hard. The first indication will likely be a cloudy pool.
Normally, you can clear cloudy pool water with pool shock. But if the cloudiness doesn’t dissipate after shocking, especially if you try it a couple of times, it could be too much calcium in the water.
If left unaddressed for too long, you may also notice a buildup of calcium sediment on pool surfaces. When that happens, it’s time—past time, really—to reduce the amount of calcium in your pool.
How to Lower Calcium Hardness in Your Pool
Once you test the water and determine the calcium level is too high, you’ll need to bring it down.
- Drain and replace some water. Before you replace the water, test your water source. If it’s high in calcium, try using a hose filter to keep some of the minerals out. Otherwise, this will be an exercise in futility.
- Use pool flocculant. If you can’t or don’t want to drain any water from the pool, try using
pool floc to clump the excess calcium. Once the clumps form, you’ll need to manually vacuum your pool to remove them. Important: Be sure to turn your pump and filter off before putting floc in the water. You do not want to get any flocculant in your filter, or you’ll need to replace the filter medium. To that end, you also need to ensure you vacuum to waste. This means you can’t use floc if you have a cartridge filter. - Try muriatic acid. If draining and floc don’t work, you can add muriatic acid as a last resort. It won’t actually reduce the water’s calcium hardness, but it will raise the saturation level, which can help bring the water back into balance.
What If the Water Is Too Soft?
How is this even possible? How can water be too soft? Well, when it’s the water in your pool, it’s definitely a concern.
Too-soft water will be corrosive to your pool. It can dissolve concrete and plaster, and corrode any metal parts submerged in or touched by the water. It all amounts to expensive repairs if you don’t bring the calcium hardness level back up.
How to Raise Calcium Hardness Levels
Good news! Bringing the hardness level up is much easier than lowering it. All you need to do is add a calcium hardness increaser to your pool. Be sure to carefully follow the instructions on the package in order to obtain the best results.
To add the proper amount of hardness increaser, you’ll need to know your pool’s volume, which you can easily determine with a pool calculator.
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How to Get It Juuuust Right
Of course, the best way to avoid any calcium hardness problems is to maintain your pool, keep the water balanced, and prevent the calcium from getting too high or too low.
- Keep your pool clean.
- Balance the water. Keeping a close eye on your pool chemistry will help you prevent problems related to calcium hardness, and a lot of other things as well.
- Test the water frequently. This is especially important if your water source is hard. Testing every week—every two weeks at most—will help you stay on top of things. Be sure to choose test strips that include calcium hardness, or get a liquid test kit.</
- Address problems early. Don’t wait for water hardness to get out of hand before you try to fix it. As soon as you see the level creeping a little too close to the lower or upper limit of the appropriate range for your pool, take action.
Tests for 7 important chemistries in seconds: Total Hardness, Total Chlorine, Total Bromine, Free Chlorine, pH, Total Alkalinity, and Cyanuric Acid.
Balancing Calcium Hardness Isn’t That Hard
It just requires some vigilance on your part. Pool maintenance just isn’t an area where you can slack off and expect things to be fine when you get back into your routine. The longer you let the water chemistry languish, the more likely it is that you’ll have trouble with calcium hardness, and any number of other things.
Owning a pool should be fun. The better you care for your pool, the less work it will be, and the more you can enjoy it.
Happy Swimming!
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- Download our FREE Pool Care Cheat Sheet: It’s a free, easy-to-use guide to help you keep track of taking care of your pool.
- The Pool Care Course: You’ll get 30+ step-by-step videos and a downloadable guide with everything you need to know about pool maintenance.
- The Pool Care Handbook: It's an illustrated guide to DIY pool care, including water chemistry, maintenance, troubleshooting, and more.
