Salt Water Pool Pros and Cons – Advice from Bob Lowry

Saltwater chlorine generators keep getting sold as a “chlorine alternative,” but the chemistry never changed: a salt pool is still a chlorine pool. You add salt, the cell applies electricity, chloride converts to free chlorine, and that chlorine sanitizes the water just like liquid chlorine or dry chlorine. The big win for many pool owners is convenience and steadier dosing, but the big misunderstanding is thinking sanitation is somehow different. A quick look at any owner’s manual reveals rated production in pounds of chlorine per day, which makes the marketing language hard to defend. For pool service techs, the practical takeaway is simple: test and manage free chlorine and combined chlorine the same way you would in any properly maintained swimming pool.

Dialing in salt level and run time is where performance and cost meet. Most manufacturers target roughly 3,000 to 3,500 ppm salt, which can mean hundreds of pounds of salt in an average residential pool. Output is controlled mostly by percent-on time, and cell life is largely a function of total hours operated, so “more runtime” is literally “less lifespan.” Adding borates can reduce chlorine demand by helping prevent algae growth, letting you lower generator output, stabilize pH rise, and reduce scale formation on the plates. The water may feel softer than traditional pools, and it is nowhere near ocean salinity, yet salt doesn’t disappear when water splashes out. When splash-out evaporates on decks, rails, slides, and water features, it leaves concentrated salt behind, and concentrated salt is corrosive, crystal-forming, and stubborn to remove without regular rinsing.

Corrosion risk climbs fast when salt is over-added or when bonding and grounding are ignored. A common service mistake happens when a system shows “low salt,” and someone keeps adding salt without verifying with an independent salt meter. Pushing salt to 5,000 to 6,000 ppm increases corrosion potential and can even reduce system performance. With salt plus total dissolved solids, the pool can behave like a low-voltage battery, which makes galvanic corrosion more likely if metals and equipment are not properly bonded and grounded. Black staining or deposits near lights, ladders, and metal fittings can be a warning sign that metal is being transported from a heater or other component. Some setups benefit from a sacrificial zinc anode that corrodes first to protect more valuable parts, but it is not a substitute for correct electrical bonding and grounding practices.

Scale and “flakes” are often blamed on phosphates, but that’s usually the wrong culprit. Flakes are typically calcium carbonate coming out of solution, not calcium phosphate, and the math matters: phosphate tests often report parts per billion, which translates to only a few parts per million. A bigger driver is heat inside the cell when water flow stops and the generator shuts down without a cool-down period, allowing calcium to precipitate. Programming a pump schedule so the generator turns off five to ten minutes before flow stops can reduce scaling, and maintaining a slightly negative LSI (saturation index) helps limit plate buildup. Finally, remember these devices produce a fixed amount of chlorine and are not on-demand. After pool parties, heavy rain, or sudden bather load spikes, there can be a window with low residual sanitizer, so pros may need to supplement with liquid chlorine and keep testing instead of relying on “boost” mode for safety.