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“Balanced Water” – What Does It Mean?

Within the profession of water-quality management, there are several subcategories of expertise needed in order to be effective. One of the most important is how to manage and maintain mineral balance in water.

“Balanced water” means water that is in a state of equilibrium. All water contains minerals, chiefly calcium, but many others as well. When it’s “balanced,” that means it does not need to absorb more minerals nor does it need to release or “precipitate” them. It is, to borrow a phrase, “at peace.”

That sounds simple enough, but it’s much more complicated. Reason being, everything in water chemistry is interrelated, and there are places where mineral balance intersects with sanitization and other key areas. Yet, at the same time, it is very much also its own science.

All of the facets of water chemistry hold hands; they all exist in a state of shifting equilibriums. It’s actually kind of a beautiful relationship, especially when everything is working. But when one part of the recipe is out of whack, it can cause a domino effect that ultimately compromises water quality and the user experience.

Balancing the Water

Mineral balance, in particular, directly impacts bather comfort, sanitizer and oxidizer efficiency, the texture and feel of the water, the appearance of interior surfaces (especially plaster), and the cost and effort required to maintain the pool. It encompasses the most basic set of pool and spa service cannons: the almighty litany of pH, total alkalinity, calcium hardness, total dissolved solids, and water temperature.

That’s a lot to consider, but fortunately, we have long had the tools to successfully manage water balance. Testing products and technology are reliable, assuming you know how to use them, and we have a wonderful system for calculating the cumulative effect of the key chemical constituents.

Specifically, all of those values I listed above comprise the enduring Langelier Saturation Index (LSI), which has been used since the 1950s to balance water across a range of applications. Originally developed for closed aquatic systems, i.e., those not exposed to the environment, such as public utility and industrial applications, the LSI was adapted to the open-air systems of pools, spas, and other types of decorative and recreational water features.

Technically speaking, in the narrowest definition, it’s an approximate measure of water’s level of saturation of calcium carbonate. In the broader, more directly applicable sense, it indicates whether water is aggressive, meaning it is deficient in minerals and will “seek” to balance itself by dissolving minerals, such as the calcium compounds in plaster. Or, conversely, how over-saturated water is with minerals causing calcium compounds and metals to precipitate out of solution in the form of scale or stains.

Without going into a formal primer on LSI calculations (information that’s widely available in other resources), suffice to say that maintaining the water as close to a zero value as possible, which is perfectly balanced water, the more stable all aspects of your water chemistry will remain. Without a working understanding of how the values that factor into the LSI all work together, water management becomes nothing more than guesswork.

Midsummer Checkup

This is why in midsummer we recommend to our clients that we conduct a full chem index. This process gives us a comprehensive understanding of all the key chemical constituents in the water. Chief among those is the water balance, specifically calcium hardness and total alkalinity. We’ve learned that those two factors can be the toughest to keep up with.

Most of the time, you don’t see the difference; the water still looks clear, but when the levels start to shift, we start hearing complaints about bather comfort and the water becomes much more difficult to manage. It’s either going to be corrosive or scaling because the pH is fluctuating and constantly bouncing back and forth. It’s amazing how a relatively minor shift in pH influences the LSI.

As technology advances, there will be more and more opportunities to take the control of water balance out of human hands. That’s a positive because as is the case with sanitizing and oxidizing, the more automated the system becomes, the more reliable and less likely you are to experience fluctuations.

It’s also worth noting that when we reduce the chlorine compounds used, the less the influence on water balance. Again, it’s all a subtle applied science that’s crucial to the work of the water quality professional.

the Water Geek


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A blog about all things water, written by SRK's founder Steve Kenny.