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Back to Basics: An Introduction to LSI and Water Chemistry

  Nov 1, 2017 / by Will Cappiello

Orenda Technologies Calcium Scaling Chemicals

If you are responsible for maintaining a swimming pool, you know that ensuring proper water chemistry is a critical part of that task. And while there are many components of water chemistry, one of the most important — and one that is often overlooked — is calcium hardness level.

Why is it so important? The answer involves both aesthetics and potential pool damage. When calcium hardness is too high, your pool water can’t keep the calcium it contains in solution. The result is that calcium “precipitates” or returns to its solid form and attaches itself to pool surfaces, appearing as an unsightly white coating known as “scale.” Although this problem is annoying, it can be corrected by adjusting the water chemistry.

When calcium hardness is too low, your pool water needs more calcium, and — this is key — it is going to get that calcium from somewhere. Water is unrelenting in this quest, and will destroy everything from your vinyl liner to your pool equipment to get what it needs. Unlike scaling, this process, known as “etching”, results in permanent damage to pool surfaces.

LSI to the Rescue

How do you know if your calcium hardness is in the right range? Fortunately, in 1936 Wilfred Langelier developed what is called the Langelier Saturation Index (also sometimes called the Langelier Stability Index). It is a method for measuring where water is in relation to its desired equilibrium of calcium and dissolved solids. In other words, it tells you whether water is scale-forming (a positive LSI) or corrosive (a negative LSI).

A perfect LSI score is zero (0.0), and the generally accepted range for pool water is -0.3 to +0.3. Water in that range will neither scale nor corrode.


Tools for Assessing and Adjusting LSIOrenda-Technologies-Pool-Dosiing-Calclulator-App.png

There are a number of tools on the market for determining how to bring your LSI back into the acceptable range. One is an app called the Orenda Pool Dosing Calculator. Orenda is a leader in water science, with a line of natural pool chemicals that are formulated to meet the strictest standards of quality and purity in the industry: NSF/ANSI Certification, Standards 50 and 60.

 The Orenda Pool Dosing Calculator allows you to enter eight variables — from water temperature to calcium to pH — and instantly see the LSI based on those current levels. Then, by modifying those levels in the app, you can see what it will take to bring an LSI that is out of the recommended range back in line. The resulting information can be reviewed in the app or emailed for future reference.

 Our LSI Series: More Information to Come

In another post, we’ll go into more detail on exactly what the Orenda Pool Dosing Calculator looks at and how it helps you maintain proper calcium hardness. In the meantime, the Latham dealer near you is happy to answer your questions about water chemistry, general pool operation and maintenance, or designing and installing the perfect pool. Give us a call!

Latham Ultraseam Vinyl Liner Ebook

Topics: Polymer Pools, Vinyl Liners, Pool Liners, In-Ground Pools

Will Cappiello

Written by Will Cappiello

Will Cappiello is the Product Director at Latham Pool Products. He loves working for Latham, the Largest Swimming Pool Manufacturer in North America.