Saltwater Pool Cheat Sheet

Six numbers run a saltwater pool: pH, total alkalinity, calcium hardness, cyanuric acid, salt and free chlorine. The manufacturer guides publish five of them. They do not publish a free chlorine range at all, which is a problem, because free chlorine is the number that actually keeps the water clear and its correct value depends on your cyanuric acid. Both tables are below, with the arithmetic shown so you can check it against your own test kit.

Target ranges

These are Hayward’s published targets, from the AquaRite owner’s manual and the Chemistry Quick Start Guide. They are the ranges your equipment was designed around, so they are the sensible default.

Note 1, the alkalinity disagreement. Hayward says 80 to 120 ppm and In The Swim uses the same window for closing a salt pool. Orenda disagrees specifically for salt pools and recommends 60 to 70 ppm. Their reason is not arbitrary. They report that most saltwater pools with white flakes have a high LSI, and most of those have a high LSI because they have too much alkalinity. If your cell flakes, that is the number to look at first. Both figures are on this page because both are defensible and they are not reconcilable.

Note 2, calcium. Hayward gives 200 to 400 ppm flat. Swim University splits it by surface, 175 to 225 ppm for vinyl and fiberglass and 200 to 275 ppm for concrete and plaster. In a salt pool, the scale risk argues for the lower half of whichever range applies to you. That last sentence is our reading, not a quoted recommendation from either source.

Note 3, and this is the important one. The salt row is a water test target, not a panel reading target. A salt cell has no salt sensor. It measures how easily current crosses the plates and infers salinity from conductivity, temperature compensated. So scale on the plates, cold water, low flow or an aged cell all move the displayed number while no salt moves anywhere. A LOW SALT warning is frequently not low salt. Test the water before you buy a bag.

Free chlorine, the number the guides leave out

Hayward’s Chemistry Quick Start Guide publishes no free chlorine range. That absence matters, because in a stabilized outdoor pool there is no single correct free chlorine number. The correct number scales with your cyanuric acid, since CYA binds chlorine and holds most of it in reserve rather than in active form.

For a salt pool, Trouble Free Pool puts the minimum at CYA x 5%, with shock level at about CYA x 40%. A manually chlorinated pool needs more, about CYA x 7.5%, because it gets chlorine in slugs rather than continuously. Pool Chem Tracker publishes the same relationship in chart form with a separate salt pool column.

Find your CYA row and read across. The multiplication is shown so you can check it.

Two things fall out of that table. First, minimum means minimum, not target. Sitting at exactly the minimum leaves no margin for a hot weekend. Second, the shock column is why high CYA hurts. At 80 ppm CYA you need 32 ppm of free chlorine to shock, which is a lot of chlorine and a long wait before anyone swims. If your CYA has crept up, reducing cyanuric acid is worth doing before the next algae bloom, not after. The dose side of shocking is on salt water pool shock, and the full grid is on our CYA chlorine chart.

Testing and timing

Our sources do not publish a weekly testing schedule, so we are not going to print one as though they did. What they do publish is how long to wait before a reading means anything, which is what people actually get wrong.

Seasonally, there is a point where the cell stops being part of the equation. Hayward’s manual says the unit stops generating below 50°F. Leslie’s puts the practical range at 50 to 60°F. Below that, your chlorine comes from the bottle. In spring, most pools need a salt booster dose of 10 to 20%, which you size against your gallons on the pool salt calculator. The weekly rhythm in between is on salt water pool maintenance, and the shopping list behind it is on salt water pool chemicals.

Troubleshooting quick reference

Everything above sits under the salt cell hub, and how we check these numbers is on how we test.

Where to go next