Salt in swimming pools

Salt-water swimming pools do have chlorine content. A salt-water pool is one that utilizes a chlorine generator. Chlorine generators have been around for decades. As technology and materials continue to evolve, chlorine generators continue to improve in performance.

Ocean water has a salt content of around 35,000 parts per million (”ppm”). Humans have a salt taste threshold of around 3,500 ppm. Most chlorine generators require a salt content of 2500 – 6000 ppm in the pool. A unit that needs less than 3500 ppm to operate effectively is optimal. If the salt content is higher, that warm, salty water will be pretty horrible!

Generally, when people swim in a non-chlorine generator pool (a pool with no salt water in it) they often notice that their skin dries quicker when they come out of the pool. They may feel and/or see whitish residual, chlorine flaking, on the skin. In a salt-water pool (one with a chlorine generator) the water feels smoother, the skin feels smooth and many people feel more refreshed.

For starting up a salt generator the usual level of salt in the water is 2500 to 3000 ppm. In a 10,000 gallon pool that would be about 200 to 250 lbs of salt. A 25,000 gallon pool would need more than 500 lbs. Always test the water for salt before adding more salt. The type of salt to use is granulated, evaporated, non-iodized salt. Be careful, many salt products contain tricalcium phosphate to prevent caking. It’s insoluble and ends up on the bottom or in the filter. Watch out for iodine. Do not use rock salt or water conditioner salt. The salt makes chlorine (technically HOCl, the killing form of chlorine and OCl-, the fairly inactive form) and sodium hydroxide and hydrogen gas. When the chlorine is used in oxidation, it becomes chloride. The chloride is recycled back to chlorine. In a perfect world, you would only have to add chloride (salt) once. However, some reactions of chlorine with organic material tie up or use up the chlorine making it unavailable to be recycled. Therefore, the water must be tested periodically to make sure the salt content is OK.

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