Understanding Cyanurate Alkalinity

If you've ever wondered why your pool chemistry calculations don't always add up perfectly, or why there's sometimes a difference between total alkalinity and carbonate alkalinity readings, you're about to discover a crucial piece of the puzzle that many pool professionals overlook: cyanurate alkalinity.

In episode 143 of the Rule Your Pool Podcast, hosts Eric and Jared tackle this complex but essential topic that affects nearly every outdoor pool. Understanding cyanurate alkalinity isn't just academic—it's practical knowledge that can help you better manage pH stability and make more accurate water balance calculations.

The Mystery Behind Total vs. Carbonate Alkalinity

For years, pool professionals have been puzzled by the difference between total alkalinity readings and the carbonate alkalinity used in LSI calculations. As the hosts explain, this confusion led to significant changes in how water testing apps present information.

Several years we used to just have all the parameters for the LSI and it used to just say alkalinity as one of them. It didn't say total alkalinity like it does now and we didn't have the secondary readings to show carbonate alkalinity... Because people didn't know which one to input because when you calculate the LSI, it's specifically asked for the carbonate alkalinity as the number you use for the factors.

— Jared, Rule Your Pool Podcast

This distinction matters because the Langelier Saturation Index (LSI) specifically requires carbonate alkalinity for accurate calculations. When you see a difference between your total alkalinity and carbonate alkalinity readings, that gap represents cyanurate alkalinity—assuming you're using cyanuric acid as a chlorine stabilizer.

Understanding Buffering Systems in Pool Water

To grasp cyanurate alkalinity, you first need to understand how buffering systems work in pool water. The hosts break down this complex chemistry into digestible concepts.

A buffering system consists of an acid and its conjugate base pair. The primary buffering system in most pools is the carbonate system, which includes carbonic acid, bicarbonate ions, and carbonate ions. This system is responsible for most of the alkalinity in your pool water.

A buffering system is basically an acid and a conjugate base pair. And the only difference between an acid and its conjugate base is the hydrogen concentration. So it either has a hydrogen connected or it doesn't.

— Eric, Rule Your Pool Podcast

When you add muriatic acid to lower pH, you're introducing hydrogen ions that bind to bicarbonate ions, neutralizing alkalinity and converting it to carbonic acid. This process demonstrates how the buffering system works to resist dramatic pH changes.

The Role of Cyanuric Acid as a Buffer

Here's where it gets interesting: cyanuric acid doesn't just stabilize chlorine—it also creates its own buffering system in your pool water. This cyanurate buffering system operates alongside the carbonate system, contributing to the total buffering capacity of your pool.

The cyanurate buffering system has its own pKa value, which determines at what pH range it's most effective as a buffer. Unlike borate, which buffers against pH rises, cyanurate alkalinity contributes to the overall alkalinity reading but behaves differently than carbonate alkalinity in chemical calculations.

If you have cyanuric acid in your pool you have an additional buffering system on top of bicarbonates in your water.

— Eric, Rule Your Pool Podcast

Why This Matters for Pool Professionals

Understanding cyanurate alkalinity has several practical implications for pool maintenance:

• More Accurate LSI Calculations: Using the correct carbonate alkalinity value instead of total alkalinity gives you more precise water balance calculations
• Better pH Management: Recognizing the additional buffering capacity helps explain why some pools resist pH changes more than others
• Improved Problem Diagnosis: When pools behave unexpectedly, cyanurate alkalinity might be a contributing factor
• Enhanced Chemical Dosing: Understanding the true buffering capacity helps you dose chemicals more accurately

The difference between total and carbonate alkalinity becomes particularly important when cyanuric acid levels are high. In pools with elevated CYA levels, the cyanurate alkalinity can represent a significant portion of the total alkalinity reading.

Practical Applications and Calculations

Modern pool chemistry apps now account for cyanurate alkalinity by showing both total and carbonate alkalinity readings. When you input your water test results, the app automatically calculates the difference and uses the appropriate carbonate alkalinity value for LSI calculations.

This automation helps pool professionals focus on water balance without getting bogged down in complex chemistry calculations. However, understanding what's happening behind the scenes makes you a more knowledgeable and effective pool professional.

The difference between total alkalinity and carbonate alkalinity is this cyanurate alkalinity. Assuming you have cyanuric acid in your pool which almost every outdoor pool does.

— Eric, Rule Your Pool Podcast

The Bigger Picture: pH Cannot Be Controlled

One of the most important concepts reinforced in this episode is that pH cannot truly be controlled—only managed. The presence of multiple buffering systems, including cyanurate alkalinity, demonstrates why pH is constantly shifting.

Hydrogen ions don't disappear when you add acid; they move between different compounds in a constant equilibrium. This movement is influenced by temperature, CO2 levels, bather load, and the various buffering systems present in your pool water.

Understanding this dynamic helps explain why pools sometimes seem to have a "mind of their own" when it comes to pH stability. It's not magic—it's chemistry, and cyanurate alkalinity is an important part of that chemical equation.

For pool professionals looking to elevate their understanding of water chemistry, grasping the concept of cyanurate alkalinity represents a significant step forward. It bridges the gap between basic water testing and advanced chemical management, providing insights that can improve both your diagnostic skills and your ability to maintain perfectly balanced pool water.

Episode Chapters

• 00:00 Introduction and Housekeeping
• 05:30 Total vs. Carbonate Alkalinity Confusion
• 10:15 Understanding Buffering Systems
• 15:45 How Cyanurate Alkalinity Works
• 22:30 Practical Applications for Pool Pros
• 28:00 Why pH Cannot Be Controlled