Optimal Chlorine Levels Saltwater Pool

Hayward’s AquaRite manual asks for free chlorine of 1.0 to 3.0 ppm, with stabilizer at 60 to 80 ppm and 80 as the target. That is the number your warranty is written against, so it is the number to start from.

It also sits uneasily next to the best known argument in amateur pool chemistry. Rather than pick a side and pretend, we will lay both out and tell you what to watch.

The chart

Read as a set, that is high stabilizer and low free chlorine at the same time. Hold that thought.

The conflict worth naming

Trouble Free Pool’s article on the free chlorine and cyanuric acid relationship argues against any fixed chlorine range. Stabilizer protects free chlorine from the sun, the free chlorine you must hold depends on your CYA level, and it rises as CYA rises. Let it drop too low for the CYA you are running and you get algae.

The two positions do not reconcile.

• Hayward gives one free chlorine band, 1.0 to 3.0 ppm, and does not move it when CYA moves. Their own CYA recommendation is 60 to 80 with 80 the target, so a pool following the manual precisely holds 1.0 to 3.0 ppm at CYA 80.
• Trouble Free Pool makes required free chlorine a function of CYA. On that logic a pool at CYA 80 needs meaningfully more chlorine than one at CYA 30, and a fixed band cannot be right at both ends.

A smaller disagreement sits alongside it. Hayward wants CYA 60 to 80, Trouble Free Pool 60 to 90 ppm for a salt water chlorine generator pool. Those overlap, so it is not a fight, but they are not the same instruction.

There is a ratio, and we have since published it. Trouble Free Pool establishes that the relationship exists and that the requirement rises with CYA, without giving a number on the page above. The CYA chlorine chart has the table: for a salt pool the minimum free chlorine works out at about CYA times 5%, against 7.5% for a pool chlorinated by hand. At CYA 80 that is 4.0 ppm, which is above the top of Hayward’s own band. That page shows the arithmetic row by row.

What to do with two answers

Follow your manufacturer’s chart, because the warranty follows the manual. For a Hayward system that is free chlorine 1.0 to 3.0 ppm at CYA 80. Then treat the band as a floor rather than a comfortable target, and use one signal to tell you whether it is too low for your pool.

Algae is the signal

This is the practical resolution. Trouble Free Pool’s point is that free chlorine too low for your CYA produces algae. So algae is not a mystery event requiring a new product. It is a measurement telling you the chlorine you hold is not enough for the stabilizer you hold.

If you test 1.5 ppm, everything says in range, and the walls are slippery by Thursday, the chart is not working for your pool. Two things move.

Raise the free chlorine you hold. Aim for the top of the band rather than the bottom and see whether the problem stops.

Or bring CYA down. If stabilizer has crept above the manual’s range, chlorine demand went with it, and stabilizer only leaves with water. Orenda’s guide to reducing CYA is blunt that draining and diluting is the most economical and practical way, with reverse osmosis effective but expensive. CYA does oxidize out eventually, but it takes months and high chlorine levels.

Chlorine tabs are the usual reason it crept up. Orenda’s figure: “trichlor is only 45.8% chlorine (by weight). The majority of it is cyanuric acid.” Dropping tabs in to help the cell out is how owners reach CYA 120 with chlorine that will not hold.

Cloudy water reads the same way. Check free chlorine against stabilizer before buying a clarifier, in the order on cloudy salt water pool.

The two levers you actually have

A salt pool has no chlorine dose. It has an output percentage and a run time, and the cell only makes chlorine while water moves through it. Daily production is roughly output percentage multiplied by pump hours.

Output percentage is the obvious dial and usually the wrong one to reach for first. Turning it up works the cell harder for the same hours, and the cell is the expensive part. River Pools puts a well maintained cell at three to seven years and $700 to $1,100 to replace, and replacements at Leslie’s reach $1,949 for a Jandy AquaPure 1400.

Pump hours are the gentler lever. More hours at a lower percentage makes the same chlorine with less stress on the plates, and better circulation with it. If you change one thing, change this one.

When free chlorine is low, in order:

1. Confirm the reading with a fresh test, not a strip out of a damp box.
2. Check CYA. Low stabilizer means the sun burns chlorine off faster than the cell makes it, and no output setting fixes that.
3. Check pH and clean the cell if the plates are crusted.
4. Add pump hours.
5. Raise output percentage last.

Cold water changes the answer

Below a certain temperature the cell stops being an option, and the number is model specific. Hayward states that “the Aqua Rite automatically stops generating when the pool water temperatures drops below 50ºF.” Orenda says most salt cells alarm or shut off between 55 and 59°F, since warmer water makes electrolysis easier. Not the same threshold, so read your own manual. In shoulder season a pool can be healthy and still show no production, and adding salt to chase it only leaves you with too much salt in June.

Super chlorinate is not a chlorine level tool

Hayward’s super chlorinate mode runs the cell at full output for 24 hours. Useful for a small catch up, but not shock. In The Swim is direct about it: most salt systems in shock mode “will only raise the FC level by a few clicks - up to 5-7 ppm. It also does it very slowly, which will not have the desired effect of killing algae, removing chloramines or pathogens.” It also “places a heavy demand on the salt cell, shortening its lifespan.”

For a real jump you add chlorine by hand. Doses are on salt water pool shock, and the products worth owning are in salt water pool chemicals.

Test properly or none of this means anything

Test free chlorine, not total, from below the surface and away from a return, weekly at minimum. Strips tell you whether you have chlorine. They will not reliably tell you whether it is 1.5 ppm or 3.5 ppm, and that difference is the entire subject of this page. The rhythm is in salt water pool maintenance, and your panel is not measuring salt either, so check it against a real test using salt levels and testing and size any dose with the pool salt calculator.

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