During one of your routine water chemistry tests, you might find out that your pool’s calcium hardness levels are off. Your research likely led you to learn that calcium chloride is effective at returning pool water to healthy calcium levels. However, you might not know how this chemical works or how to use it.
I’m here to put your worries aside and equip you with the knowledge to single-handedly get your pool’s calcium hardness levels back on track.
- Hard water has too much calcium, whereas soft water has too little; both can be detrimental to your pool’s health
- Calcium chloride helps to boost calcium levels in soft water
- Make sure to carefully calculate how much calcium chloride to add to the pool water
- Wear protective gear and ensure that you pour the calcium chloride into a bucket of pool water and not the other way around
Why Calcium Hardness Matters
Calcium is vital to the health of your swimming pool because it helps to balance the chemical makeup of your water. Therefore, when your swimming pool has the correct calcium concentration (calcium hardness), it prevents you from spending extra money on products to keep other chemical water fluctuations in check.
Ideal Calcium Hardness Levels
Finding a balanced calcium hardness level can be difficult, but it benefits your pool environment.
You want to maintain a calcium hardness level of about 200-400 parts per million.
Anything over 400 ppm risks hard water that can damage the pool and equipment. Anything less than 200 ppm can bring the pool alkalinity down, corrode objects in the swimming pool, and irritate swimmers’ skin and eyes.
Hard Water vs. Soft Water
When water is “hard,” it contains calcium and other minerals like magnesium. While you want these minerals in your pool, if the water has too much calcium, you’ll encounter issues with scale building up in the plumbing and lining of your pool. If you’re dealing with this issue, read my guide on how to remove calcium scale deposits from your pool.
On the other hand, water that’s “soft” happens because it’s lower in minerals such as calcium. Rain and local, untreated water are examples of soft water.
Unfortunately, too much soft water damages pools because the water clings to any calcium it encounters. As a result, metal pieces and grout in your pool may corrode.
What is Calcium Chloride and How Does it Work?
Calcium chloride is a chemical effective at boosting calcium levels in pool water. As its name implies, its chemical makeup contains calcium.
If you have too little calcium in your pool and don’t apply calcium chloride, you’ll notice that grout, concrete, and any other calcium-containing surfaces the water touches begin to deteriorate. That’s because the water is extracting calcium wherever it can find it.
For that reason, calcium chloride is critical—it literally feeds your water the calcium it lacks.
Calcium chloride is also vital to pool health because it helps the water stay balanced. By having a healthy calcium level, combined with a proper pH, total alkalinity, and total dissolved solids, your pool will be ideal for swimming.
To be fair, calcium chloride isn’t the only way you can introduce calcium into your pool; calcium hypochlorite (cal-hypo for short) is an alternative that can be used.
However, cal-hypo isn’t as effective as calcium chloride because it’s easy to add too much calcium, making your pool go from having issues with soft water to problems with hard water.
How to Add Calcium Chloride to Your Pool
Follow the manufacturer’s instructions, and you’ll instantly know the results.
As I mentioned above, the ideal range for calcium in pool water is 200 – 400 parts per million (ppm).
Remember—calcium chloride is to treat pools with low calcium levels. If you discover that your pool suffers from a high calcium concentration, you’ll need to shock your pool and possibly add water or muriatic acid. Head to my article on muriatic acid for your pool if you’ve never used this chemical before.
Assuming you have a case of low calcium on your hands, follow the steps below to get your pool back into shape.
Step 1: Prepare Your Pool
I understand the temptation to dump calcium chloride in your pool straight away, but it’s vital that you first prepare your pool.
To do so, test your water’s pH, total alkalinity, and chlorine. Each of these numbers should fall within the following ranges:
- pH: 7.4 – 7.6
- Total alkalinity: 80 – 120 ppm
- Chlorine: 1 – 3 ppm
You shouldn’t have issues testing for these three items if you own a digital tester. However, if you buy test strips, double-check to make sure the test includes them.
Should you discover that any of these items are outside the recommended range, rest easy. They’re easy to fix by using the right products to counterbalance them.
After properly balancing your pool water, you’re ready to start addressing its low calcium issue.
Step 2: Calculate the Amount of Calcium Chloride
You’ll need to know the following to calculate how much calcium chloride you should put in your water:
- Current calcium hardness (in ppm)
- How many gallons of water are in your pool
As a general rule, for every ten ppm of calcium, your pool water needs to increase; you should add two ounces of calcium chloride per 1,000 gallons of water.
Phew, that’s a mouthful! Let me break it down for you.
Let’s say you need to increase your calcium levels by 30 ppm, and you own a 20,000-gallon pool.
That means you’ll need to divide 30 ppm by ten ppm, which equals 3 ppm. Then, multiply three by two ounces (for 1,000 gallons of water), which gives you six. That’s the number for 1,000 gallons of water.
Given that you have 20,000 gallons of water, you need to multiply six by 20, which gives you 60 ounces of calcium chloride that you’ll need to add to your pool water.
Step 3: Get Your Gear Ready
With the calcium chloride calculations under your belt, the hardest part is over. However, this next step is critical to ensure you stay safe during the application process.
On its own, calcium chloride isn’t a very harmful chemical. But when you add it to water, it becomes extremely hot—it could even burn you if you’re not careful.
For this reason, you must wear appropriate clothing to stay safe. You should wear a well-fitted pair of goggles, a long sleeve shirt and pants, and gloves with chemical-resistant properties.
According to a study on soft tissue necrosis, calcium carbonate rarely causes skin issues in its salt form. However, the heat released when calcium chloride mixes with water can cause burns and calcium deposits on the skin.
Step 4: Prepare the Mixture
You should not dump the calcium chloride directly into your pool. Instead, grab a five-gallon bucket and fill it about 75% with water from your pool. With your calculations in hand, pour the appropriate amount of calcium carbonate in ounces into the bucket.
Here’s the calcium chloride I recommend to most of my clients.
This is my go-to calcium chloride. "Hardness Increaser" is just a fancy name for the same thing.
Make sure to pour slowly because of the hot chemical reaction the calcium carbonate will have. Furthermore, remember to never pour water on top of calcium carbonate. For your safety, always put pool water in the bucket first, followed by the chemical.
Step 5: Add the Calcium Carbonate to Your Pool
With your pool pump turned on, circle the circumference of your pool and gradually pour the calcium carbonate mixture into the water.
There are a few things to keep in mind during this time. First, this mixture can destroy a pool’s finish, so be careful to keep it from splashing up on the sides. Secondly, brush the sides of the walls after you pour in the substance to help move the solution around the water.
After waiting for a complete cycle, re-test your water. If the calcium hardness level is within the 200 – 400 ppm range, you can use your pool again.
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What is a Calcium Hardness Increaser?
Many pool stores will advertise a calcium hardness increaser as a product that can be used to raise your calcium hardness level. These products are generally much more expensive than calcium carbonate, but if you look at the ingredients, they are usually made of the same thing.
Watch out for products like this because they are essentially calcium carbonate in a much more expensive package. The one I linked above from Pool Mate is marketed as “Calcium Hardness Increaser,” but is still decently affordable.
And that’s about it for calcium chloride, an effective chemical for boosting the calcium level in your swimming pool. If your calcium hardness is too high, check out my research on how to lower calcium hardness. Any questions? Let me know.