Alkalinity Deconstructed w/ Sarah the Pool Girl

If you've ever stared at your pool chemistry test results wondering what alkalinity actually means and why it matters, you're not alone. Many pool owners know they need to test for it, but few understand the crucial role alkalinity plays in maintaining crystal-clear, balanced water. In this deep dive into pool chemistry, we'll uncover the mystery behind alkalinity and show you how to master this fundamental aspect of pool maintenance.

What Is Alkalinity Really?

Let's start with the basics. When pool professionals talk about alkalinity, they're referring to something more nuanced than you might expect. As Sarah from the Talking Pools Podcast explains:

For me, that means it's the amount of bicarb in the pool... I just manipulate alkalinity with acid and bicarbs.

— Sarah, Talking Pools Podcast

While Sarah's practical approach focuses on the bicarbonate (bicarb) that she uses to adjust alkalinity, the technical definition goes deeper. Andrew, her co-host, provides the scientific perspective: alkalinity is a quantitative measure of the dissolved alkali in the water. Think of it as your pool's chemical buffer system – the thing that keeps your water chemistry stable and prevents dramatic swings that could damage your pool or make swimming unpleasant.

But here's where it gets interesting: there are actually different types of alkalinity measurements. Most pool owners only know about total alkalinity, but understanding carbonate alkalinity can give you much more precise control over your water balance.

Total vs. Carbonate Alkalinity: The Game Changer

This is where pool chemistry gets sophisticated. When you test your pool's alkalinity with standard test strips or kits, you're measuring total alkalinity. However, this reading includes more than just the bicarbonates that actually buffer your pH. It also includes contributions from cyanuric acid (your pool's stabilizer).

Carbonate alkalinity gives you a more accurate picture of your water's true buffering capacity. Here's how to calculate it:

So to get the carbonate alkalinity, you take the total alkalinity minus the stabilizer times a third. So you take that stabilizer reading and basically times it by a third... And then you do alkalinity minus that. And that will give you the carbonate.

— Andrew, Talking Pools Podcast

This calculation becomes especially important when your pool has high stabilizer levels. Sarah shared a real-world example of a pool where this made all the difference:

The reading was 160, and then the total alkalinity was like 100, okay? But the carbonate alkalinity was like under 50. It was like 48 or something like that. That's way off. It's very acidic.

— Sarah, Talking Pools Podcast

In this case, despite having a total alkalinity reading of 100 (which seems acceptable), the true carbonate alkalinity was dangerously low at 48, leading to plaster etching. This is why understanding both measurements is crucial for proper pool care.

Why Alkalinity Matters for Your Pool

Alkalinity serves as your pool's pH bodyguard. It creates what experts call a "pH ceiling" – a buffer that prevents your pH from swinging wildly up or down. This stability is crucial for several reasons:

• Surface Protection: Proper alkalinity prevents etching of plaster, tile, and other pool surfaces
• Equipment Longevity: Balanced water protects your pumps, heaters, and other expensive equipment
• Swimmer Comfort: Stable pH means no burning eyes or skin irritation
• Chemical Efficiency: Your sanitizers work more effectively in properly balanced water

The seasonal aspect of alkalinity management is something many pool owners miss entirely. In summer, when temperatures rise, you want lower alkalinity (around 80 ppm) to prevent scaling. In winter, you'll want to raise it to around 120 ppm to prevent surface etching when the water becomes more aggressive.

How to Manipulate Alkalinity Like a Pro

Managing alkalinity comes down to two main chemicals: sodium bicarbonate (bicarb or baking soda) to raise it, and muriatic acid to lower it. Here are the practical guidelines:

Raising Alkalinity:

• Use sodium bicarbonate (the same as baking soda, just in larger quantities)
• About 1 pound of bicarb raises alkalinity by 10 ppm in a 10,000-gallon pool
• Add it slowly and allow circulation before retesting

Lowering Alkalinity:

• Use muriatic acid (always follow safety protocols)
• Approximately 1 gallon of muriatic acid lowers alkalinity by 40 ppm in a 20,000-gallon pool
• Never change alkalinity by more than 40 ppm at once

Sarah emphasizes the importance of gradual adjustments:

When you do change your alkalinity, don't change it more than 40 ppm at a time. It's just, it's too much acid at one time, you know.

— Sarah, Talking Pools Podcast

For precise dosing, consider using an acid demand test with your Taylor test kit or a reliable pool calculator app rather than guessing.

Seasonal Alkalinity Strategy

One of the most overlooked aspects of pool chemistry is how seasonal changes affect your chemical balance. Temperature is actually one of the most significant factors in water chemistry, yet many pool owners maintain the same alkalinity year-round.

Summer Strategy (80 ppm):

• Lower alkalinity prevents scaling when temperatures rise
• Helps maintain stable pH despite increased bather load and evaporation
• Works in conjunction with proper calcium hardness levels

Winter Strategy (120 ppm):

• Higher alkalinity prevents surface etching when water becomes more aggressive
• Compensates for reduced chemical activity in colder temperatures
• Essential for protecting plaster and tile during the off-season

Sarah admits she learned this lesson the hard way:

My first winter, I didn't know that you had to raise your alkalinity. I thought you just left it there, you know. I knew about bicarb, but I didn't know how to use it... I just kind of left my alkalinity where it was for the most part.

— Sarah, Talking Pools Podcast

The Calcium Connection

Here's an advanced tip that can transform your pool maintenance: the relationship between alkalinity and calcium hardness. If you're confident your calcium hardness is in the proper range (300+ ppm), you can push your alkalinity lower in summer – even down to 60 ppm – for exceptional pH stability.

This strategy offers several benefits:

• Dramatically reduces acid consumption throughout the summer
• Prevents scaling issues
• Can actually resolve existing calcium buildup problems

However, never attempt low alkalinity without first ensuring proper calcium levels. If you don't regularly test calcium hardness, stick to the standard 80-120 ppm alkalinity range.

Putting It All Together

Mastering alkalinity is about understanding it as part of your pool's complete chemical ecosystem. It's not just another number to keep in range – it's the foundation that allows all your other chemicals to work effectively. By understanding the difference between total and carbonate alkalinity, implementing seasonal strategies, and coordinating with calcium hardness, you'll achieve the kind of water balance that makes pool maintenance effortless.

Remember, alkalinity management is a skill that develops over time. Start with the basics: maintain 80-120 ppm total alkalinity, adjust seasonally, and make gradual changes. As you gain experience, you can explore more advanced techniques like carbonate alkalinity calculations and precision dosing. Your pool – and your wallet – will thank you for the investment in proper water chemistry knowledge.

Episode Chapters

• 00:00 Introduction to Alkalinity
• 03:45 Defining True Alkalinity
• 08:20 Carbonate vs Total Alkalinity
• 15:30 Manipulating Alkalinity with Chemicals
• 22:10 Seasonal Alkalinity Management
• 28:45 The Calcium-Alkalinity Connection