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Frequently Asked Questions > Salt Water Pools and Pristiva┬« > I read that one supplier of salt claims their products is at least 99% pure. If it is this pure, how can the choice of salt make a difference in swimming pools?

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If you were only adding a small amount of salt say like table salt, it would likely not matter. But that is not the case. Salt is added to fresh water pools at levels of 3200 to 4000 ppm. To put this in perspective, an average 22,000 gallon in ground pool will require 533 pounds of salt to achieve 3200 ppm of salt at start up. That requires over 13 bags of salt weighing 40 pounds each be hauled to pool side and distributed over a relatively brief period.

All salt suppliers claim their salt is high purity however the simple fact is that adding 533 pounds of anything to a swimming pool doesn’t require a significant percentage of impurities present to become meaningful in its impact to pool water chemistry. While many salt suppliers boast they have no additives, Mother Nature has made her own contribution.

  • At 99 % salt purity, 5.3 pounds of impurities are introduced to a 22,000 gallon pool at start up alone!
  • 5.3 pounds of impurities equates to adding ~ 29 ppm of unknown stuff into the pool
  • If only 5% of the impurities were iron, this would equate to ~ 1.5 ppm iron…more than sufficient to cause discolored water and possible staining of pool surfaces
  • Even at 99.9 % purity over ½ pound of impurities are added to the pool

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