You work hard to keep your pool clean, so you may be startled to wake up one day and notice that a white layer formed around the edge of your swimming pool. Calcium scale is a common issue pool owners face. Unfortunately, not only is it aesthetically displeasing, but calcium scale can leave permanent stains on your pool wall if you don’t take care of it soon enough.
In this guide, I’ll give you background on how calcium scale forms, how to get rid of it, and what you can do to prevent it. Assuming you caught the problem early, you should be able to reclaim your pool walls without long-term damage.
What Is Calcium Scale?
Calcium scale is a white-gray chalky build-up that forms along the waterline of pools. It coats your beautiful blue pool tile or lining, dulling its color and making your pool look more aged than it is.
Aside from being unpleasant to the eye, calcium buildup has a rough texture as it builds up. As a result, it can cause discomfort, scratches, and snagged bathing suits when you’re hanging around the edge of your pool.
Calcium scale occurs when calcium turns from a liquid to a solid. It then congregates on surfaces, favoring the waterline of your pool. The most common reason for calcium carbonate formation is because your pool has a high calcium hardness level and pH level.
Unfortunately, a pool’s waterline isn’t the only place where calcium scale can build up — this pesky residue favors filters, too. So, if the issue has been going on for a while, it may have already partially clogged your filters.
Although many pool owners identify the issue of calcium scale once they notice the calcium carbonate building up on the edge of their pool, there’s often an earlier sign — cloudy water. If you happen to catch calcium scale in this phase, it’ll be easier to treat the problem.
Types of Calcium Scale
As if having calcium scale isn’t enough of an issue for pool owners, the scale comes in two varieties — calcium carbonate and calcium silicate. Let’s take a look at each.
If your pool has to have calcium scale, cross your fingers that it’s the calcium carbonate variety. With a brighter white and flaky texture, calcium carbonate is easier to remove than calcium silicate.
Testing for calcium carbonate is easy once you purchase muriatic acid from your pool shop. Simply mix a few drops of the acid with a deposit of your water and wait to see if it reacts. If the acid reacts with the foam, you know that you’ve got yourself a calcium carbonate issue.
Unlike calcium carbonate, calcium silicate has a greyer hew. Calcium silicate takes a longer time to build on a pool wall than its carbonate sister. Unfortunately, that means that if you find calcium silicate on your pool wall, then it likely already inundated your filtration system, causing the phenomenon called pipe scaling.
We’ll talk about how to remove calcium silicate shortly, but for now, know that if you have a major calcium silicate problem, you may need the support of a professional to help you out.
You can test for calcium silicate the same way you do calcium carbonate—by using muriatic acid to see if there’s a reaction. If there’s no reaction, then you know that the film on your pool wall is from calcium silicate.
Step-By-Step Process for Removing Each Type of Calcium Scale
They may feel like the same problem, but removing calcium carbonate and calcium silicate requires different techniques once you go through the initial steps to check for scale. I’ll walk you through each so you can start tackling your calcium scale today and get back to enjoying your pool. However, let’s first look at the general steps you’ll need to follow.
Step 1: Test the Water
Unfortunately, you’ll need to temporarily say goodbye to your daily swims until you test the water to determine the cause of your calcium scale. In addition to using muriatic acid to determine the type of calcium scale your pool has, you also need to test the pH and calcium levels.
If there’s too much calcium in the water or the alkalinity is too high, you’ll need to get these levels back to normal to prevent future issues. I’ll cover how to do this in the next few steps.
Step 2: Lower the Calcium Hardness
The most effective way to remove calcium from your water is by draining a portion of your pool and refilling it. You should aim for your pool to have a calcium level between 200 – 400 ppm. Anything higher than 400 ppm can cause scale and cloudy water.
Step 3: Get the Alkalinity Back in Balance
Once you’ve refilled your pool and have the calcium levels under control, it’s time to focus on your water’s alkalinity. Your pool should be in the 80 – 120 ppm alkaline range. If it’s higher than 120 ppm, you can use dry or muriatic acid to lower it. You’ll need to follow the instructions to see how much acid you need to use according to your pool size.
Step 4: Check the pH Level
Ideally, your pool water should be within a 7.4 to 7.6 pH range. However, pools often range in pH from 7.2 to 8.-0. As a word of caution, don’t let your pool’s pH level go too low—it can corrode the metal parts of your pool system and damage plaster. If it is too low, read my guide on raising pH in your pool.
Step 5: Use a Cleaner and Scrub
Now that you addressed the route of the issue, it’s time to remove all that unwanted calcium scale from your pool wall. You can use a combination of scale eraser, scale remover, and scrubbing to eliminate the white film. I’ll talk more about the effectiveness of these shortly.
Step 6: Enjoy Your Pool!
Your pool is ready for you to use again. At the end of this article, I’ll show you strategies for preventing a calcium scale problem in the future.
But for now, let’s take a closer look at how to remove calcium carbonate and calcium silicate from your pool individually.
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How to Remove Calcium Carbonate
With the relative relief that the calcium scale on your pool is only from calcium carbonate, it’s time to tackle the issue. You can use three different tools to remove the calcium carbonate from your pool wall:
- Pumice stone
- Stain eraser
- Scale remover
Pumice stone is the most natural way to approach the issue, so it’s an excellent option for people who don’t want to add chemicals to their pool water. However, because pumice stone is abrasive, you should never use it on soft-sided pool liners; tile and concrete are the best fit.
When using a pumice stone, it’s essential to keep the surface you’re rubbing wet. Otherwise, you could leave permanent scratches on your pool wall.
If you choose to use a stain eraser, you’ll apply it directly to the white calcium carbonate line around your pool. You can read the manufacturer’s instructions for the specific steps on how to proceed with this.
For a longer-term solution, you can purchase a calcium scaling treatment. The solution works by treating all the water in your pool, dissolving the calcium carbonate deposits over a few weeks.
How to Remove Calcium Silicate
Calcium silicate is more stubborn to remove than calcium carbonate. But with a lot of elbow grease, you might be able to get your pool looking like new again.
Using a pumice stone is the most effective way to remove the deposits. Remember, you should keep the surface wet and only use the stone on hard surfaces like tile and concrete.
If you have a vinyl or fiberglass pool, you can try to use a calcium scaling treatment as I described with calcium silicate. However, the downside is that this treatment can take months to start working if it makes any impact at all.
The good news is that pool providers often have stronger chemicals that better tackle calcium silicate. So, you may want to call a professional if these other strategies don’t work for you.
How to Prevent Calcium Scale
The key to preventing calcium scale is ensuring your pool water maintains the right balance of calcium and pH levels. You can use a few strategies with your standard pool maintenance to ensure your swimming water stays in tip-top shape. They include:
- Monitor the pH of your water. You should aim to stay within a 7.4 to 7.6 pH range.
- Cover your pool regularly or purchase an automatic pool cover since evaporation speeds up the production of calcium deposits.
- Install a reverse osmosis water treatment. That way, it’ll remove calcium carbonate and calcium silicate before they build up.
Any pool owner who has a calcium scale problem will agree that it’s inconvenient and damaging to their pool. Luckily, there are ways to reduce or remove these calcium deposits significantly. Once you take care of the initial problem and implement the prevention methods I discussed here, you’ll enjoy countless summers of fun in your calcium scale-free pool.
Questions? Let me know.