Is the Orenda Calculator™ true to the LSI formula? Or different?

Have you ever wondered why different pool chemistry calculators give you slightly different LSI readings? Or questioned whether the tools you're using to balance your pool water are truly accurate? In this deep dive into the science behind pool chemistry calculations, we'll explore the fascinating history of the Langelier Saturation Index and uncover why precision matters more than you might think when it comes to keeping your pool water perfectly balanced.

A Hard-Learned Lesson in Scientific Accuracy

The story begins with a humbling experience that shaped Orenda's approach to scientific accuracy. Eric Knight recalls a pivotal moment from 2017 when the company learned the importance of verifying every piece of information they publish:

I sat in what I did not realize at the time was a competitors class... They said that phosphates weaken chlorine because phosphates take the hydrogen from H O Cl and make it the weaker form of chlorine. And we ran with it because it was in my notes many times back in the day... We got eviscerated for putting that out.

— Eric Knight, Rule Your Pool Podcast

This experience transformed their methodology completely. Knight explains that ever since this incident, they have been "extraordinarily cautious" and now "not only double-check our work, we triple-check it and quadruple check it and we try to cite everything." This commitment to accuracy became the foundation for their approach to developing the Orenda Calculator.

The Genius Behind the Langelier Saturation Index

To understand why calculator results differ, we need to go back to the beginning. Dr. Wilfred Langelier, a professor of sanitary engineering at UC Berkeley, first published his groundbreaking formula in 1936 in the Journal of the American Water Works Association. What many pool professionals don't realize is that Langelier was working on drinking water systems, not swimming pools.

Dr. Langelier was ahead of his time, working on the cutting edge of water disinfection when typhoid fever and the Spanish flu made water safety a critical public health concern. His goal was to calculate exactly how to treat water to deliberately create a thin protective film of calcium carbonate on the inside of iron or galvanized pipes.

His formula is pH minus pH s sound simple... the pH s is the pH at which a water of a given calcium content and alkalinity is in equilibrium. Neither over nor under saturated with calcium carbonate. It is based upon three well known mass law equations and one stoichiometric equation.

— Eric Knight, Rule Your Pool Podcast

Despite Langelier describing his equation as "extremely simple to use," the reality is far different. The original formula involves complex mathematics with thermodynamic constants, ion pairs, and supersaturation calculations that would challenge even chemistry professionals.

From Complex Science to Practical Charts

The evolution of the LSI from Langelier's original work to today's pool industry tools is a story of necessary simplification. Here's the timeline:

• 1936: Langelier publishes the original formula for drinking water systems
• 1942: Larson and Buswell adapt the formula to parts per million and add ionic strength corrections
• 1964: Van Waters and Rogers adapt the formula for open water systems like swimming pools
• 1965: Carrier creates reference charts to make the formula accessible to non-scientists

The creation of reference charts was revolutionary because it made the LSI accessible to pool professionals without advanced degrees in chemistry. However, this accessibility came with a trade-off: precision.

The Limitation of Reference Charts

Traditional reference charts, while invaluable for bringing LSI calculations to the masses, have inherent limitations. They require rounding to specific values, which introduces imprecision into calculations. For example, if your calcium hardness is 45 ppm, but the chart only shows values for 25, 50, and 75 ppm, you're forced to estimate.

Knight and Morgan explain this limitation:

There was a lot of rounding when you have a chart like that. You have to round either up or down. We didn't like that. There was not a lot of precision and so we interpolated between the factors.

— Eric Knight, Rule Your Pool Podcast

When you're dealing with six or seven different factors (temperature, pH, calcium hardness, alkalinity, cyanuric acid, TDS, and potentially borates), these small rounding errors can compound, leading to less accurate results.

Why the Orenda Calculator is Different (and More Accurate)

The Orenda Calculator doesn't rely on simplified reference charts. Instead, it uses the actual mathematical formulas, updated with modern thermodynamic constants and adapted for swimming pools with cyanuric acid. This approach offers several advantages:

• Precision: No rounding required - you can input exact values
• Updated Science: Uses thermodynamic constants refined over the past 88 years
• Pool-Specific: Properly accounts for cyanuric acid and other modern pool chemicals
• Technology-Enabled: Leverages computing power to perform complex calculations instantly

The team emphasizes that their approach isn't about creating something new, but about staying true to Langelier's original scientific principles:

We have technology on our side. We have spreadsheets and pivot tables and all kinds of things we can build into a formula that make it more accurate or more precise. We don't need to be limited by reference charts that can fit on a page.

— Eric Knight, Rule Your Pool Podcast

The Science Behind the Precision

The mathematical foundation of the Orenda Calculator comes from peer-reviewed scientific literature, particularly the work of John Wojtowicz, whose research papers are cited in ANSI/APSP standards. This isn't proprietary math created by Orenda - it's established science that's been adapted for practical use in swimming pools.

The key difference is that instead of forcing users to work within the constraints of printed charts, the calculator performs the actual mathematical operations that Langelier intended. This means accounting for:

• Precise temperature corrections
• Exact calcium hardness values
• Accurate alkalinity measurements
• Proper cyanuric acid adjustments
• Ionic strength corrections

Each of these factors plays a crucial role in determining whether your water will be scale-forming, balanced, or corrosive.

Practical Implications for Pool Professionals

What does this mean for pool service professionals and pool owners? The difference between chart-based calculations and formula-based calculations might seem small, but it can have significant practical implications:

• Chemical Dosing: More accurate LSI calculations lead to more precise chemical adjustments
• Equipment Protection: Better balance means less risk of scale formation or corrosion
• Water Quality: Properly balanced water feels better and requires fewer chemicals
• Cost Savings: Accurate calculations prevent over-treatment and under-treatment

The goal isn't to criticize traditional reference charts, which serve an important educational purpose and remain valuable tools. Rather, it's about recognizing that when precision matters - particularly for professional applications - formula-based calculations provide superior accuracy.

The Commitment to Transparency

Perhaps the most important takeaway from this discussion is Orenda's commitment to transparency and scientific rigor. After their early experience with misinformation, they've built a culture of verification and peer review. Every piece of information they publish is backed by citations and reviewed by multiple experts.

This approach serves the entire pool industry by ensuring that the tools and information available to professionals are as accurate and reliable as possible. In an industry where precision matters for both safety and water quality, this commitment to scientific accuracy benefits everyone.

The debate over calculator accuracy ultimately comes down to a choice between convenience and precision. Reference charts will always have their place as educational tools and quick references, but when you need the most accurate LSI calculation possible, formula-based tools like the Orenda Calculator provide the precision that Dr. Langelier intended when he first developed this groundbreaking index nearly 90 years ago.

Episode Chapters

• 00:00 Introduction and Episode Overview
• 02:30 Learning from Past Mistakes
• 08:15 The History of Dr. Langelier's Formula
• 15:45 Evolution from Formula to Charts
• 22:10 Why the Orenda Calculator is Different
• 28:30 The Science Behind the Precision
• 35:00 Practical Implications for Pool Professionals