LSI History Anyone??

[Spa Owner]

I have been thinking about something and its bothering me.

If I read enough pool books I will find reference to use of potassium permanganate and lime prior to about the 1920's when calcium hypochlorite became the sanitiser of choice.

I can go back to 1936 and find Dr Langelier's paper which started all the various saturation indexes.

Somewhere in the past I read the pool store, as a stand alone shop selling chemicals and equipment only, came into being in the USA around 1978.

What I cant read or haven't seen anywhere is when and why the pool industry adopted the LSI and its derivatives. How did this happen and why? And as importantly when?

 

[JoyfulNoise]

See here - Langelier and Calcite Saturation Indices (LSI and CSI)

LSI has been modified over the years and is more of an empirical formula rather than one derived from first-principles. CSI is derived from first principles (chemical thermodynamics) as so is more accurate in my opinion. Neither of them, nor any chemical index for that matter, can tell you the rate of the reaction occurring or what is required to get the reaction going, they only simply tell you if the reaction is possible.

 

[Spa Owner]

Its not that. I am researching the origins. I want to find out why it was adopted.

 

[JoyfulNoise]

I don’t believe there’s a clear answer to that question. The pool industry is full of a lot of borrowed science that is not at all applicable to pools. LSI probably came through heater manufacturers who borrowed the concepts of calcium saturation from the industry of boiler and cooling tower operators. In closed systems, some small amount of calcium carbonate scale is beneficial. In a swimming pool and pool heater, calcium carbonate scale is not really all that desirable. It’s essentially a misuse of the theory and then simply tacked on along the way by repetition. You’d be hard-pressed to find any specific instance of its adoption.

Nowadays we know a lot more about pool water chemistry, cementious pool surface and how to best control scale and corrosion. The calcite saturation index is most applicable to pools and should be the standard but the pool industry as a whole is very resistant to any form of change.