Scaling: What causes it and how to prevent it

While it’s annoying, scaling is something that will happen in your pool from time to time. Whether it’s the rocks, the plaster or the tile on the surface, scaling can leave a white calcium mark or residue that can detract from the aesthetics of the pool. While scaling on plaster, tile or bricks isn’t harmful to the foundation of your pool, it does leave it looking less attractive.

How does scaling occur? How do you deal with it once it happens? And better yet, how do you prevent it from happening in the first place? We’ll answer these questions one by one in this article.

wall with scaling

Scaling, as you can see in the picture above, typically shows up as a white film or mark on the surface and is visible once a wet surface is dried. It varies in degree and severity and can range from anywhere to a slight disturbance to a huge hassle that causes plenty of headaches and consternation.

Causes of scaling

There are two main causes of scaling, one which occurs naturally with an imbalance of moisture and one that occurs when the water chemistry of pool isn’t diligently maintained.

  • Efflorescence: Don’t worry if you can’t pronounce it, it’s a tough one. It’s also tough to get out of concrete, as efflorescence is a crystalline deposit that comes from salt gravitating to the surface of concrete or masonry to create a white, film-like coating. Efflorescence scale can be caused simply by a gradual moisture imbalance in a section of your pool.”The moisture causes the salts to emerge through the gunite and rise to the surface,” said Scott Gordon, the Branch Manager of Sales at Master Tile. “These salts need somewhere to go, and efflorescence is the result of that. You’ll see it happen on bricks of a house if a sprinkler keeps hitting them at a certain point.”
  • Water chemistry imbalance: Having the wrong pH and alkalinity is another main cause of scaling in pools, as it leaves more of a calcium deposit on your plaster and tile than a salt-based one. Having the water slightly out of whack allows there to be too much calcium in the pool, which latches on to the pool surface and leaves a white scale residue. Too little alkaline can have a similar effect, leaving the unsightly white film.

Preventing/Dealing with Scaling

The best way to deal with scaling is not to allow it to happen in the first place. Gordon believes that taking the initiative with water chemistry is essential in preventing scale from occurring in the first place.

“It’s up to the homeowner to keep their pH levels where they need to be,” he said. “If you don’t pay attention or neglect it, your pH will go too low and too high and scaling will occur, and once it occurs, it’s very difficult to remove. You can try to scrub it out, but it usually comes back right after. Having the correct water chemistry is key.”

You can use smart maintenance systems such as IntelliChem and ScreenLogic to keep your water chemistry on point. As detailed in the writeup on IntelliChem that we did in July, the IntelliChem system not only helps you keep your chlorine, alkalinity, cynaric acid and calcium where they should be, but they can also tell you whether your pool water is ideal, normal, corrosive or scaling. If your water is the latter, than that’s when that tricky white film starts to appear.

It’s also good to scrub the surface of your pool regularly. That will help break up any calcium or salt deposits that make it to surface before they start leaving their mark on that surface. See point No. 1 in this article — scrubbing works with scaling as well as algae.

As far as correcting current scaling, the best way to go is to make sure your water chemistry is where it needs to be. There are other possible solutions that can be considered such as scrubbing out the white film or using chemical and glass beads to blast it out, but that scale will return if the water chemistry isn’t what it should be. If you want to keep your pool looking good, learning water chemistry and implementing it is absolutely necessary.


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Ultimate Pools has been a leader in pool building and outdoor improvements in Magnolia, The Woodlands and Southeast Texas since 1991, specializing as a pool builder since 1999. From pools, waterfalls, hot tubs, decks, outdoor kitchens and outdoor improvements, Ultimate Pools will provide the highest of quality and customer service to you. Surf our website, send us an email, give us a call at (936) 321-9632, or visit our offices at 5170 FM 1488, Magnolia, TX 77354 today!

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