You work hard to keep your pool clean, so you may be startled to wake up one day and notice that a white layer has formed around the edge of your swimming pool. Calcium scale is a common issue in pools that is aesthetically displeasing and can leave permanent stains on your pool walls.
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.
Main Takeaways
- Calcium scaling is a white chalky buildup that typically occurs when the calcium hardness in your pool water is high.
- The main way to lower your calcium hardness level is to partially drain and refill the water.
- The best way to remove calcium scale from your pool walls is to scrub it with a pumice stone or a stain eraser.
What Is Calcium Scale?
Calcium scale is a white-gray chalky buildup many pool owners may unfortunately become familiar with. It coats your beautiful blue pool tile or lining, dulling its color and making your pool look more aged than it is.
The unsightly scale happens 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 that your pool has high calcium hardness and pH levels.
How to Identify Calcium Scale
Before we dive into treating this issue, the first step is to identify the calcium scale. After all, there’s no point in treating the stain if it turns out it’s not calcium scale at all!
You can easily identify calcium scale by the telltale white or gray residue generally left on the waterline of your pool. However, it’s worth noting that, 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.
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 hanging around the edge of your pool.
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 catch calcium scale in this phase, it’ll be easier to treat the problem. Head to my article on how to clear a cloudy pool for tips on treating this problem as well.
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.
Calcium Carbonate
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 you’ve got a calcium carbonate issue.
Calcium Silicate
Unlike calcium carbonate, calcium silicate has a grayer hew. Calcium silicate takes longer to build on a pool wall than its carbonate sister. Unfortunately, that means that if you find calcium silicate on your pool wall, it has likely already inundated your filtration system, causing 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, you know 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 must also 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.
This expansive test kit includes nine tests for most pool chemical measurements you need.
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. You can read my article on lowering high calcium hardness for more detailed notes.
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.
You can get Leslie's Dry Acid (sodium bisulfate) online if you don't have a Leslie's Pool Supplies store near you.
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 the pH in your pool.
Step 5: Use a Cleaner and Scrub
Now that you addressed the root 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 this in detail 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 so that you don’t have to deal with this pesky issue again!
But for now, let’s take a closer look at how to specifically remove calcium carbonate and calcium silicate from your pool.
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, keeping the surface you’re rubbing wet is essential. Otherwise, you could leave permanent scratches on your pool wall.
If you choose to use a stain eraser, 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 has any impact.
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.
Get My Free Pool Care Checklist
Download my free, printable pool maintenance checklist to help you accomplish regular pool care tasks for any type of swimming pool.
Frequently Asked Questions
Do you need to acid wash to get rid of calcium deposits?
Depending on the type of calcium scale deposits you have in your pool and the severity of the issue, you may need to use muriatic acid to get rid of calcium deposits. However, as a general rule, you should be able to get rid of these pesky white deposits with some elbow grease and a pumice stone.
Can you use vinegar to remove pool calcium?
Vinegar is an excellent household product you can use to treat a variety of issues in your pool, including calcium deposits. Simply spray a solution of one part vinegar and one part water onto the affected area, and scrub, scrub, scrub!
Enjoy Your Scale-Free Pool
Any pool owner with 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.
Do you have any more questions about dealing with calcium and other types of stains? Let me know. I’ll be happy to help!
