Winterize Salt Water Pool

Closing a salt pool is closing a regular pool plus two jobs: getting the cell out of the plumbing before it can freeze, and ignoring the salinity number on your panel while you do it. The second matters more than it sounds, because fall is when the display starts under-reporting and owners start adding salt they do not need.

First, the cell has already stopped working

Cold water is harder to electrolyze. Orenda’s explanation is that warmer water makes electrolysis easier and colder water takes more energy, and that most salt cells alarm or shut off between 55 and 59°F. Hayward states it for its own unit: “The Aqua Rite automatically stops generating when the pool water temperatures drops below 50ºF.”

Those figures do not agree, and they are not meant to. Orenda describes the general population of cells, Hayward describes one product. Yours has a cutoff somewhere in that band and the only way to know it is your manual.

The consequence is not model specific. Sometime in the fall your generator stops making chlorine while the pump still runs and the pool still looks open. Warm October, swimmers in the water, and you are chlorinating by hand from that point on. Liquid chlorine from the salt water pool chemicals list is the way to do it.

Second, the salt reading will fall, and no salt has gone anywhere

Internalize this before you buy a single bag in October.

Your panel has no salt sensor. It passes current across the cell plates, measures how easily it crosses, and infers a salinity figure with a temperature correction. Poolside describes most systems as estimating “salt levels using an algorithm” rather than reading salinity directly.

Two things happen at once in the fall. The water cools, which reduces conductivity, and the season’s worth of scale is at its thickest, which also reduces conductivity. The panel’s temperature compensation is a correction, not a measurement, and it is calibrated for a clean cell. Stack a cold pool on a scaled cell and the displayed number drops, the LOW SALT light comes on, and nothing has happened to the actual salinity of your water.

Owners on Inyo’s guide to reducing salt describe what happens when the display is believed: “I added to much salt to my 15000 gallon pool because I did not realize my T-cell was going bad.”

So before you close, test with a salt titration kit, not the panel. Orenda recommends verifying with a separate salinity meter, since a faulty sensor can read lower than actual. If your own test puts you inside Hayward’s “2700-3400 ppm (parts per million) with 3200 ppm being optimal,” you are fine whatever the panel says. If it genuinely is low, the pool salt calculator gives you the bags, and salt levels and testing covers reconciling the two numbers.

Salt does not evaporate and does not get used up. Between closing and opening it can only leave with water, and the pool is covered. A pool that reads 3,200 in September and 2,400 in November did not lose salt.

Balance the water before you close

Do this while the water is still warm enough that things dissolve.

• pH 7.2 to 7.8 and total alkalinity 80 to 120 ppm, per Hayward’s chart. Water sitting all winter at high pH spends the winter depositing scale.
• Stabilizer in your manufacturer’s range. Hayward asks for 60 to 80 ppm with 80 as the target; Trouble Free Pool recommends 60 to 90 ppm for a salt chlorine generator pool. Follow your own manual, and do it a week before closing, since stabilizer dissolves slowly.
• Free chlorine at the top of range, since the cell will not be topping it up.
• Shock only if the pool is dirty. Doses and the stabilizer adjustment are on salt water pool shock.

Clean the filter, vacuum, and brush. A pool closed dirty opens green, and that is why people find themselves reading about a cloudy salt water pool in May.

What to do with the cell

Turn the generator off at the panel first, so nothing tries to fire while the water is draining out of it.

Remove the cell. Shut the valves, unplug the cable at the union, and take the cell out of the plumbing. Water left between the plates can freeze and crack the housing. This is a component that runs $700 to $1,100 to replace, or $1,949 for a Jandy AquaPure 1400 at Leslie’s, so the ten minutes is worth it.

Rinse and inspect. Flush it with a garden hose and look at the plates. Hayward’s guidance is to try a high pressure hose first for mild deposits, and only go to a 4:1 solution of water to muriatic acid, soaked “for a few minutes” and rinsed, if there is real scale. ALWAYS ADD ACID TO WATER, NEVER ADD WATER TO ACID, and never put a metal tool between the plates, because it scratches the coating and the coating is the cell. Full method on how to clean a salt cell.

Do not acid soak a clean cell just because it is off the pool. Every unnecessary soak takes coating off plates that only have so much to give.

Store it dry and indoors. Drain it, let it dry, cap the ends, and put it somewhere that does not freeze.

Fit the dummy cell if your system came with one, or use the union plugs, so the plumbing is closed.

Freeze protection for everything else

In freezing regions Hayward’s instruction is to drain all water from the pump, the filter, and the supply and return lines. Blow the lines, plug the returns, drop the water below the skimmer or use a skimmer plug, drain the pump and filter, and pull the drain plugs. Standard pool closing, and none of it changes because there is salt in the water. Salt water does not protect plumbing from freezing in any way you should rely on.

Mild winters, where you keep it running

If you never freeze, you may leave the pool open with the pump on a reduced schedule. Two things to plan for. The cell stops generating once the water drops below its cutoff, so budget for liquid chlorine through the cold months. And the panel will complain about salt, so ignore it and rely on your own test. Neither is a fault. This is the cold weather behavior of a system that works by conductivity, and it is the same reason spring opening produces false alarms. More in salt water pool maintenance and on the cell itself at salt cells for pools.

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