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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.
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.
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.
A simple but effective liquid test kit for chlorine pools and hot tubs.
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.
Once you test the water and determine the calcium level is too high, you’ll need to bring it down.
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.
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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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.
Tests for 7 important chemistries in seconds: Total Hardness, Total Chlorine, Total Bromine, Free Chlorine, pH, Total Alkalinity, and Cyanuric Acid.
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!
Matt is the founder of Swim University. He's been in the pool industry since 1993. His mission is to make pool care easy for everyone. Each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
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