How to Test the Cyanuric Acid Level In Your Pool (5 Easy Steps)

Cyanuric acid helps to regulate the chlorine in your pool, so keeping tabs on how much is in your water is essential for proper sanitation.

Not enough cyanuric acid and your chlorine will be unprotected against sunlight, causing it to be consumed too quickly. Let it get too high and you risk locking up too much of your chlorine, significantly reducing its sanitizing power.

This article will cover step-by-step how to test the cyanuric acid level in your pool water using either a test strip or a liquid test kit.

Did you know? Cyanuric acid goes by many names in the pool industry, including pool stabilizer, chlorine stabilizer, and pool conditioner. It’s also commonly abbreviated to CYA.

What’s the Ideal Cyanuric Acid Level in a Pool?

Generally, the ideal cyanuric acid level for an outdoor swimming pool is between 30 and 50 parts per million (ppm).

But it’s not quite as simple as that.

The optimal cyanuric acid level should scale with your free chlorine level. The above range assumes you keep your free chlorine level between 1 and 3ppm. If your free chlorine level tends to sit higher, so should your chlorine stabilizer.

As a rule of thumb, your free chlorine level should be no lower than 7.5.% of your cyanuric acid level at any time, which means you should aim a little higher than that to account for natural chlorine loss between top-ups.

Note: In either case, you may need considerably less cyanuric acid if your pool is shaded or covered to prevent direct sun exposure. Since every setup is different, it can take some trial and error to find the sweet spot.

What About the Cyanuric Acid Level in a Saltwater Pool?

Generally, the ideal cyanuric acid level for a salt pool is higher at between 60 and 80 parts per million (ppm).

Why should the CYA level be higher in salt pool, you ask?

Well, this is because saltwater generators produce chlorine at a slow pace, which means they struggle to maintain an adequate chlorine level when large amounts are being burnt off by sunlight – especially at peak times of the day.

As a result, it needs a little more protection than usual, putting the optimal ratio of free chlorine in a saltwater pool at no lower than 5% of the cyanuric acid level.

Test Strips or Drops to Measure Cyanuric Acid?

Both liquid test kits and strips can be used to measure the cyanuric acid level in a pool. As with most pool water parameters, the best test to use will always depend on whether you value efficiency or accuracy the most.

A test strip can get you a CYA reading in just a few seconds, and while it won’t be laser accurate, it’s often close enough to help you navigate a pool season without issue.

Those who prefer a more scientific approach, or who own a pool that’s more prone to chemistry-related issues, will benefit from using a liquid test kit, of which there are actually two variants.

The first is a traditional liquid reagent drop test, such as those found in the popular Taylor testing kits. This is a very accurate test, but it’s fairly time and resource-intensive.

The second is what’s known as the “black dot test”, made by Pentair. This isn’t quite as accurate as the Taylor test, but it only takes a fraction of the time to carry out and proves to be a lot more reliable than a test strip.

Overall, given how much faster and simpler it is compared to a traditional liquid test, the black dot test is the one we recommend using.

How to Test Cyanuric Acid using the Black Dot Test (Recommended)

The steps below are based on the Pentair cyanuric acid liquid test kit, otherwise known as the black dot test kit.

Here’s how to test cyanuric acid in a pool using a liquid test kit:

1. Fill the Tube up to Line A

Using the provided tube, take a small water sample from the edge of your pool.

If your pool water happens to be dirty or cloudy, it’s recommended you first address the cause before attempting this test as water clarity is essential for an accurate reading.

Avoid submerging the tube directly in front of return jets that could contain higher concentrations of pool chemicals. You should also avoid pulling water from dead spots such as near steps or behind ladders.

The sample should line up with point A on the tube. Be sure to check this measurement on even ground before moving on.

2. Add the Solution to Line B

Next, grab the cyanuric acid solution (provided with the Pentair kit).

Carefully pour the solution into your water sample until it reaches line B on the tube. Be sure to pour slowly and on a flat surface to prevent adding too much solution, as this may result in having to start the test over.

Also, keep your back to the sun while doing this part. Direct UV exposure can interfere with the mixture in the tube and produce a less accurate result.

3. Mix the Solution Using the Handle

To mix the solution, simply use the handle on the tube.

You can lift the handle up and push it back down using a plunging motion. Do this 8-10 times, then let the mixture settle for a minute.

You’ll know you’re ready for the next part when the water looks slightly cloudy.

4. Lower the Handle Until the Black Dot Disappears

Now it’s time to perform the black dot test.

Start by holding the tube at waist height (or putting it on a surface at about the same distance), and then lift the handle up so you can clearly see the black dot.

Then, slowly lower the handle until the black dot completely disappears, ensuring you maintain consistent lighting conditions throughout this process. Stop dropping the handle at the exact point you no longer have visibility of the black dot.

Note: Don’t stare at the dot for too long before attempting this, else it’ll create a visual imprint and you’ll think you’re still seeing it when you’re not.

5. Take a Reading from the Meter

Finally, while holding the handle in place, take a reading of your cyanuric acid by checking where the sample waterline stops on the meter.

If the waterline is just below a certain point, always round up. This will ensure you add a little more free chlorine than is probably necessary, which is always preferable in the event of uncertainty.

Note: This particular kit should give you roughly 10 uses before needing to buy more solution.

How to Test Cyanuric Acid with a Pool Test Strip (Not Recommended)

The steps outlined below are based on the AquaChek pool testing strips, but most test strips follow the same process regardless of brand.

Here’s how to test cyanuric acid in a pool using a test strip:

1. Submerge a Test Strip

The first step is to get a test strip wet.

Most pool owners prefer to dip directly into their pool. While this can work, the surface level isn’t always representative of your pool water as a whole, so pulling a sample from below the water surface and dipping into that is recommended.

Either way, just be sure to keep the colored parts of the strip submerged for several seconds while only holding the white parts. Any direct skin contact with the colored pads will void the test and require a new strip.

2. Wait for the Chemicals to React

Place the wet strip on a dry, flat surface and refrain from shaking or blowing it.

It will take around 20 to 30 seconds for the chemicals on the colored pads to finish reacting to your pool water. You should see the color pads begin to shift in tone as this process takes place.

If nothing happens after 60 seconds, something went wrong and you will need to repeat the test with a different strip.

3. Check the Strip Against the Chart

The last step is to compare the colors on the strip to the provided color chart, which you’ll find on the back of the AquaChek strip container.

With these particular strips, the cyanuric acid reading is the very last color on the strip (closest to where you hold it), but the position of each parameter may be different depending on the brand.

A solid orange color is what you want to see for an ideal reading, with light orange and deep purple showing low and high readings, respectively. 

How Often Should You Test Cyanuric Acid?

You should test your cyanuric acid (pool stabilizer) once per week until you have a firm understanding of your water chemistry.

Once you begin to understand how your water reacts to natural and chemical changes, particularly in terms of your free chlorine level, you can reduce your CYA testing to as little as once per month.

Unlike pH, alkalinity, or chlorine, your cyanuric acid level isn’t going to move very much over time, so unless your pool experiences massive water loss or heavy dilution, you can afford to carry out this test more infrequently.

Your Stabilizer Level Matters

For most pool owners, regardless of whether it’s for a traditional chlorine pool or a saltwater pool, managing cyanuric acid is non-negotiable.

If you want your chlorine level to be able to withstand UV light while remaining effective at fighting contaminants, you need to get used to testing your cyanuric acid level on a semi-regular basis, and learning how to adjust it accordingly.