By Marcelle Dibrell
Sanitation and water balance are the twin goals of pool water chemical maintenance. One protects the bather; the other protects the surfaces and equipment.
We need to know that the water is safe to swim and relax in. We want to know that we are getting the best performance out of the sanitizers and chemicals that we are adding to the water. But we’d also like to know that the water is not corrosive, leaching material from the shell, plumbing and equipment. We’d like to be sure that the water will not deposit scale.
It is through testing that we achieve the assurance we need by providing the answers to these questions. Chemical testing is the only sure way to determine both the safety and the manageability of the water provided to the customer. Armed with the results of the tests, a good service professional can compare those results to industry standards to decide what changes must be made to bring the pool into compliance.
But truly responsible water maintenance goes beyond industry standards, because there are times when even these can let you down. Previous articles have explored the complex relationship between cyanuric acid and chlorine. Depending on the amount of cyanuric acid present, it may be necessary to add more chlorine than the currently accepted industry standards to prevent certain problems like algae.
Maintaining water balance is also more complicated than simply adhering to industry standards. It requires an understanding of the complex interrelationships between the various water balance parameters. And the most widely accepted theory of water balance is expressed by the Langelier Saturation Index. The Saturation Index uses six water balance factors to determine whether water chemistry is ideal for surfaces and equipment. By taking into account the effects of pH, temperature, calcium hardness, total alkalinity, cyanuric acid, and total dissolved solids, the pool operator can be sure that the water will be neither corrosive nor scale-forming.
The math involved in calculating ideal LSI values is a little tedious, but fortunately, there are many online LSI calculators that can assist in ensuring that water is within ideal range. (See this issue’s Straight from the Maker). And among their many merits, these calculators illuminate that simply following industry standards does not in itself guarantee balanced water.
Consider the difference in the water chemistry of a swimming pool maintained in the summer months, compared to the same pool in the winter. Such a pool may be perfectly balanced in the summer, but by changing only the temperature, become extremely corrosive come winter. (see table) Using the Langeleir Saturation Index makes it possible to attain truly balanced water. But the first step is knowing what the water parameters actually are: the fundamental reason for chemical testing.
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