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    Different values: The Ryznar Stability Index correlates higher values with more corrosive water, and lower values with water that is potentially scaling. Its value range is also different from that used by the Langelier Saturation Index.

When Cynthia Wilson noticed a persistent leak in a commercial heater she’d been servicing, she did what any pool service technician would do — called the manufacturer to request fulfillment of the warranty. But when the manufacturer’s investigator performed a water analysis, the results caught Wilson off-guard.

“Their evaluation worksheet said that we’d failed to maintain the necessary [calcium hardness] levels for the equipment warranty to cover the damage,” said the vice president of operations at Like New Pool Services Inc. in San Diego.

“Even though our water was balanced according to the Langelier Saturation Index, it was considered corrosive by the Ryznar Stability Index.”

This development would likely have thrown most service people for a loop.

Within the pool industry, the Langelier Index is taught almost exclusively, and many service veterans remain unaware that any other water balance indices even exist. “The Ryznar Index is basically not taught by anybody, except that it’s sometimes briefly mentioned in certified pool operator classes,” said Alison Osinski, Ph.D., president of Aquatic Consulting Services in San Diego.

Nevertheless, several heater manufacturers have advocated or required the use of the Ryznar Stability Index for years. Though these manufacturers also tend to promote the Langelier Saturation Index, some pool chemistry experts say the two indices aren’t always compatible. “These two formulas can conflict,” Osinski said. “They’re looking at the same issues, more or less — but the Ryznar Index wants you to have much higher calcium hardness.”

Representatives of companies that support the Ryznar Index explain that this higher calcium hardness mediates the water’s potentially corrosive effects on metals. “The Ryznar Index is oriented toward protecting equipment’s metallic surfaces, whereas the Langelier Index is focused on protecting the calcium of the pool shell,” said Rich Murphy, national pool sales manager at Lochinvar, a heater manufacturer whose warranty specifies the use of both the Ryznar and Langelier Indices.

While the Langelier Index is geared to prevent either scaling or etching, the Ryznar Index is designed to allow a slight coating of calcium to accumulate on metallic equipment, where it acts as a protective insulator.

But therein may lie the problem. “In Southern California, our water already contains too much calcium,” Osinski said. “That buildup causes all kinds of issues with oversaturation, and it clogs up our pipes, and coats our heater elements, and damages equipment.” Thus, Osinski and others have pointed out, adding additional calcium to bring the water into Ryznar-acceptable balance could lead to excessive calcium scaling in some cases.

This leaves service techs like Wilson feeling caught between a rock and a hard place. For other pool professionals concerned about a situation like this, experts agree the safest bet is to become familiar with the equipment’s warranty paperwork — and if the manufacturer mentions the Ryznar Stability Index, to try to keep the water balanced into the range where both the Langelier and Ryznar indices will consider it to be noncorrosive.

“If you maintain a Langelier Index value of 0.0 to +0.5, you’ll be right in the Ryznar Index’s ideal range,” said Kim Skinner, co-owner of Pool Chlor in Livermore, Calif.