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Magnesium, Salt & the Truth About Water Testing with LaMotte – Part 1

Is your salt test really measuring salt?

What happens when magnesium enters the equation?

And why do two different salt tests sometimes give two completely different answers?

This week on Mondays Down Under, Lee and Nick welcome Hieron from LaMotte for a fascinating deep dive into modern water testing, magnesium pools, calcium hardness, Langelier Saturation Index (LSI), and why understanding your test results is just as important as performing the test itself. 

Whether you're servicing pools every day or managing a retail water testing lab, this episode explains why blindly trusting numbers without understanding the chemistry behind them can cost your customers money—and shorten the life of their equipment.

In This Episode

•  Why total hardness is no longer the same as calcium hardness
•  How magnesium changes water chemistry 
•  Why magnesium hardness must be separated from calcium hardness 
•  The relationship between hardness and the Langelier Saturation Index (LSI)
•  Why pH remains the single biggest factor affecting water balance 
•  Does magnesium actually affect scaling? 
•  Understanding the difference between conductivity salt meters and reagent-based salt testing
•  Why two salt tests can produce dramatically different readings 
•  The hidden problem of "dead" salt and elevated TDS 
•  When water replacement becomes the only practical solution 
•  Protecting expensive salt chlorinator cells through accurate testing 
•  Why experienced technicians ask questions instead of simply printing reports 
•  The psychology of educating customers and building long-term trust 
•  A preview of LaMotte's upcoming professional training course for the pool industry 

Key Takeaways

One of the biggest myths discussed is that all salt readings are equal.

Traditional conductivity meters measure the electrical conductivity of dissolved solids, while LaMotte's Spin system chemically measures usable chloride ions—the portion of salt that can actually produce chlorine. Understanding that distinction can dramatically improve troubleshooting and help explain why older pools often experience chlorination issues despite appearing to have sufficient salt. 

The conversation also explores why magnesium pools require technicians to think differently about hardness testing. Magnesium contributes to total hardness but should not simply be substituted for calcium when calculating water balance or the LSI. Accurate testing allows professionals to properly determine true calcium hardness instead of relying on outdated rules of thumb. 

Beyond chemistry, the discussion focuses on customer communication. The best technicians don't simply hand customers a printout—they ask better questions, interpret the results, educate pool owners, and build relationships that last for years. 

Featured Guest

Hieron – LaMotte

•  Water chemistry specialist 
•  Professional water testing educator 
•  Expert in Spin water analysis technology 
•  Developer of LaMotte's upcoming online professional training program 

Coming Next Week

Part Two continues the conversation with even more practical discussions on professional water analysis, advanced chemistry, and improving customer outcomes through better testing and education. 

Listen, subscribe, and join the conversation wherever you get your podcasts.

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