When To Add Stabilizer To A Pool (and How!) | Halogen Supply

Adding pool stabilizer—also known as cyanuric acid (CYA)—is essential for protecting your chlorine from the sun’s UV rays. Without it, chlorine dissipates rapidly, leaving your pool vulnerable to bacteria and algae growth. But using too much stabilizer can be just as problematic, diminishing chlorine’s ability to sanitize effectively. In this guide, we’ll explain when to add stabilizer, how to use it properly, and why monitoring your CYA levels is critical to pool health.

Ideal Cyanuric Acid Levels for Pools

For most outdoor pools, the ideal range for cyanuric acid is 30–50 parts per million (ppm). This level provides enough protection to prevent chlorine loss from sunlight without interfering with its ability to disinfect. Saltwater pools may require a slightly higher range of 60–80 ppm, depending on the system manufacturer’s recommendations.

Indoor pools typically don’t require stabilizer, since there’s no sunlight to break down chlorine. It’s important to note that CYA doesn’t evaporate or break down easily—it accumulates over time. The only reliable way to lower high CYA levels is to partially drain and refill the pool with fresh water.

When to Add Stabilizer

There are several common scenarios when it makes sense to add stabilizer to your pool. One of the most frequent is at the beginning of the swim season, especially if you’ve just refilled your pool or performed a partial drain. Heavy rainfall or topping off your pool with fresh water can also dilute CYA levels, making it necessary to test and rebalance.

Switching from stabilized chlorine products (like trichlor or dichlor) to unstabilized options (such as liquid chlorine or calcium hypochlorite) can also result in lower stabilizer levels over time. In any of these situations, it’s a good idea to test your water before deciding whether to add more.

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How to Add Pool Stabilizer Correctly

When adding stabilizer, start by testing your CYA levels using a reliable pool test kit. Based on your readings, calculate the appropriate dosage, typically listed on the stabilizer product label or available via online dosage calculators.

Most powdered stabilizers are slow-dissolving. To speed things up and avoid residue settling in the pool, pre-dissolve the stabilizer in a bucket of warm water before adding it. With the pool pump running, pour the solution slowly into the skimmer or directly into the deep end of the pool. Let the pump circulate the water for at least 24 hours.

Keep in mind that it can take 24–48 hours for the stabilizer to fully dissolve and register on test strips or kits, so don’t retest immediately after application.

What Happens If Stabilizer Levels Are Too High?

Because CYA builds up and doesn’t degrade naturally, frequent use of stabilized chlorine can cause your levels to creep too high. This can lead to a condition known as chlorine lock, where chlorine is present in the water but ineffective at sanitizing. In these cases, algae or cloudy water may occur even when your chlorine levels seem “normal.”

To fix high CYA levels, you’ll need to drain a portion of your pool water and refill with fresh water to dilute the concentration.

Keep Your Pool Balanced All Season Long

Maintaining proper stabilizer levels is key to protecting your chlorine and keeping your pool clean, safe, and swim-ready. By understanding when and how to add pool stabilizer—and how CYA levels impact chlorine effectiveness—you can avoid common pitfalls like overstabilization or chlorine inefficiency.

Halogen Supply offers a full range of high-quality pool stabilizers and testing kits to help you stay on track. Whether you’re opening your pool for the season or troubleshooting chlorine loss after heavy rainfall, we’ve got the products and guidance you need. Contact our pool experts for personalized advice.