Unstabilized Chlorine for Pools

Unstabilized chlorine is chlorine that arrives with no cyanuric acid attached to it. There are three forms of it in the pool world. Liquid chlorine and calcium hypochlorite are the two you buy, and the third is the one you already own, because a salt cell makes unstabilized chlorine every hour the pump runs.

That third item is why this page matters more to a salt pool owner than to anyone else. Your cyanuric acid level does not creep up on its own. It goes up when you put it there, either as a bag of stabilizer or as a stabilized product. If your CYA is climbing and you have not deliberately added stabilizer, something in your routine is stabilized and you have not noticed it.

What the word actually describes

“Stabilized” on a chlorine label tells you what else is in the container, not how strong the chlorine is.

Cyanuric acid is the stabilizer. Trouble Free Pool puts it simply: stabilizer, or CYA, protects your free chlorine from the sun. A stabilized product is chlorine sold pre-mixed with that protection. An unstabilized product is the chlorine on its own.

The trade-off is direct. Unstabilized chlorine in water with no CYA sits in full sunlight and does not last the afternoon. Stabilized chlorine solves that on day one and then keeps solving it forever, because the chlorine is consumed and the CYA is not. It accumulates, dose after dose, and it only leaves when water leaves.

The three forms

Liquid chlorine, which is sodium hypochlorite. No CYA, no calcium. In The Swim names it as one of the two products to use on a saltwater pool, at 5 gallons per 10,000 gallons for a full shock. It leaves a little salt behind, which here is not a complaint. It is heavy, and it loses strength in the garage, so buy it fresh and buy it for the job in hand.

Calcium hypochlorite, cal hypo. Also unstabilized, sold as granules, 3 lbs per 10,000 gallons for a full shock. The name is the warning label: it leaves calcium in the water permanently, and calcium is what drives scale onto cell plates. Orenda notes that scale forms on the cathode side of the cell during electrolysis. With soft fill water that is a fair trade. In a pool that already runs hard, it is a slow tax on the most expensive component you own.

The cell. Your generator splits dissolved salt and produces chlorine directly in the plumbing. No CYA, no calcium, nothing accumulating. That is the quiet advantage of the whole system, and most owners never have it put to them in these words: you own a chlorine source that adds nothing you will later have to drain out.

The contrast that makes the point

Put a trichlor tablet next to those three. Orenda’s figure is blunt: “trichlor is only 45.8% chlorine (by weight). The majority of it is cyanuric acid.”

Slightly more than half the weight of a tab is stabilizer. Run a floater all season and you are not dosing chlorine with a side of CYA, you are dosing CYA with a side of chlorine. That is the mechanism behind almost every high-CYA reading in a residential pool, and it is why a salt pool that has never seen a tablet can hold the same stabilizer number for years.

If your question is specifically about tablets, which ones exist without stabilizer and whether a salt pool should use any, that is the whole of chlorine tablets without CYA.

Unstabilized chlorine still needs stabilizer in the water

This is where people get turned around. Choosing unstabilized chlorine does not mean running at zero CYA. It means you set the CYA level yourself instead of letting a product set it.

Salt pools want a fair amount of it. Trouble Free Pool recommends 60 to 90 ppm for a salt water chlorine generator pool, against 30 to 60 ppm for a pool chlorinated by hand. Hayward’s chart asks for 60 to 80 ppm with 80 as the target. They do not match exactly. Follow your own manual, because the warranty follows the manual.

You get there once, with a bag. HTH’s instructions put 1 lb per 10,000 gallons at roughly 10 ppm of CYA, added slowly to the skimmer with the pump running, no backwashing for 48 hours, 24 to 48 hours of circulation before a retest. Buying and dosing it is on chlorine stabilizer for pool. After that, unstabilized chlorine tops up the sanitizer without touching the number you just set.

What each source actually leaves behind

Only one row has a “yes” you cannot undo cheaply. Orenda’s guidance on getting CYA back down is that two things work: draining and diluting, the most economical and practical way, and reverse osmosis, effective and expensive. CYA does oxidize out on its own, but “it takes months and high chlorine levels.”

The number that follows from your CYA

Once CYA is set, it decides how much free chlorine you have to hold. Pool Chem Tracker’s chart, which reproduces the Trouble Free Pool methodology as a table, puts the minimum for a salt generator pool at about CYA times 5%, lower than a hand-dosed pool “because the generator continuously replaces what’s consumed.”

At CYA 80 that minimum is 4.0 ppm. Hayward’s own chart asks for free chlorine of 1.0 to 3.0 ppm while asking for stabilizer of 60 to 80 ppm. Follow both lines literally and you are below the minimum for the stabilizer level Hayward specified. That is a real disagreement between two authorities, not a rounding error, and the practical test is whether you get algae. The full table is on optimal chlorine levels saltwater pool and the arithmetic on the CYA chlorine chart.

If you are under that floor, the fix in a salt pool is usually more pump hours rather than a jug, and the order is on how to increase free chlorine in salt water pool.

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