What cyanuric acid does
Cyanuric acid (CYA), also called stabilizer or conditioner, acts like sunscreen for your chlorine. Ultraviolet light from the sun breaks down free chlorine very quickly — without stabilizer, an outdoor pool can lose most of its chlorine in just a couple of hours. CYA bonds loosely with chlorine and shields it, slowing that loss so your sanitizer lasts far longer.
This makes CYA essential for outdoor pools. With the right level, you use less chlorine and your levels stay stable through a sunny day. Indoor pools generally don't need it because there's no UV exposure.
The ideal cyanuric acid range
For most outdoor chlorine pools, aim for 30–50 ppm. Saltwater pools often run a little higher, around 60–80 ppm, because the salt cell generates chlorine continuously and benefits from extra protection. Below about 30 ppm, chlorine burns off too fast in sunlight; above roughly 80–100 ppm, chlorine becomes sluggish and ineffective.
Think of it as a balance: enough CYA to protect chlorine, but not so much that it handcuffs it. Staying in the recommended range keeps chlorine both protected and active.
Why too much CYA is a problem
When cyanuric acid climbs too high, it over-binds the chlorine and reduces its ability to sanitize — a state often called 'chlorine lock.' Your test may show chlorine present, but it can't do its job, so algae and bacteria gain a foothold even with seemingly normal readings.
High CYA creeps up over time because stabilized chlorine products (trichlor tablets and dichlor shock) add a little CYA with every dose. If you rely on tablets, your stabilizer slowly accumulates until chlorine stops performing. This is one of the most common hidden causes of stubborn algae.
How to raise or lower cyanuric acid
To raise CYA, add a dedicated stabilizer (cyanuric acid granules or liquid conditioner) according to the label and your pool volume. Granular stabilizer dissolves slowly, so be patient and avoid re-dosing too soon — it can take a day or more to register fully on a test.
Lowering CYA is harder: there's no effective chemical that removes it, so the practical fix is to partially drain and refill with fresh water to dilute it. If your tap water is low in CYA, replacing a portion of the pool brings the level down proportionally. To avoid high CYA in the first place, alternate stabilized tablets with unstabilized chlorine like liquid chlorine or cal-hypo.
Keep CYA and chlorine in balance
Cyanuric acid and chlorine work as a pair — the right ratio keeps your pool clear with minimal effort, while the wrong one causes endless frustration. Test CYA every few weeks, especially if you use tablets, and adjust before problems start.
PoolHakr tracks your cyanuric acid alongside chlorine and the rest of your chemistry from a single photo of your test strip, and tells you exactly when it's drifting out of range.
Let PoolHakr do the math for you
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