Cyanuric Acid: The Complete Guide


What is cyanuric acid?

Cyanuric basically works as a sunscreen for your pool, preventing chlorine in your pool from getting burned off by the sun.

It usually comes in a dry form, and it is also called a stabilizer, a conditioner, or CYA.

You can find cyanuric acid in several different forms, such as liquid, a solid granular, dichlor, or trichlor form.

How does cyanuric acid work?

Cyanuric acid was first invented in 1829. In its molecular form, cyanuric acid has a hexagonal shape with nitrogen and carbon atoms.

Nitrogen atoms are able to bond with up to three chlorine atoms.

When chlorine atoms are attached to nitrogen atoms, they are protected from the sun.

How to raise cyanuric acid in your pool?

If the cyanuric acid level is too low in your pool, your pool water will have a tough time holding onto chlorine, which means you’ll use up a lot more chlorine.

Measure your pool cyanuric acid level with your test kit, and if your pool CYA level is low, I suggest you go online or go to a pool supply store and pick up a 5 lb bucket of dry cyanuric acid.

Remember, it’s also known as a conditioner or pool stabilizer. If you get a bucket that’s labeled as either one of those names, be sure to read the labels to confirm that it is indeed cyanuric acid.

After you get your CYA, you want to turn your pool filter on while your pump is running. You want your pool system to be running when you are adding chemicals.

Next, go to a skimmer basket and open the skimmer lid. Don’t forget to check for critters because those things can sting. Empty your skimmer basket and put it back in.

You will then take one pound of cyanuric acid and dump it into the skimmer basket while your pump is running.

Your CYA will dissolve in the water. Don’t forget to keep the pump running and wait for about two hours.

You can then go back out to the pool and test your pool CYA level again after two hours.

If the test strip shows it’s between 30 to 100 parts per million, you’re good.

If your pool CYA level is still below that, then repeat the process, making sure you only use one pound of CYA at a time.

You do not want to oversaturate your water with cyanuric acid. 

If you are at around 30 parts per million, I wouldn’t worry too much about it. This is especially true if you’re using chlorine tablets because you’ll have a little bit of cyanuric acid released into the pool with the chlorine tablets’ dissolution.

Cyanuric acid saltwater pool

Raising cyanuric acid in the saltwater pool follows the same process as adding CYA to the regular pool. One thing to note is that the optimal level of CYA in the saltwater pool is slightly higher at around 80 ppm.

So keep that in mind as you raise the CYA level in your saltwater pool.

Cyanuric acid reducer

If your cyanuric acid is too high, chlorine in your pool will also be ineffective. The water molecule in your pool will become saturated, and it won’t hold any more chlorine. So, too much cyanuric acid has the same effect as too low CYA in your pool.

If your CYA level is in the high range of 150 to 300 ppm, the only way to deal with that much saturation is to dilute it. In other words, you want to get fresh unsaturated water into your pool.

There are three ways you can dilute your pool CYA level. One is through evaporation, which usually isn’t enough to get the job done. 

You can also backwash your pool if your pool has the system for it, but it’s still not enough in most cases.

The best way to do it is to drain and refill your pool with fresh water.

In case you have high total dissolved solids, changing your pool water is the only solution.

That said, if you don’t over add cyanuric acid into your pool, you should not have to change your water out any more than every three to five years or so.

All in all, there’s really no chemical you can add to your pool to effectively lower your pool CYA level, no matter what people may say.

There’s one thing you want to keep in mind if you are about to drain your pool water. You don’t want to drain your pool in the heat of summer when the sun can dry out your plaster and cause cracks in it. This can cause leaks into your reinforcement bar underneath it and do some costly damage to your pool.

So I suggest you don’t drain and refill your pool during the hot summer months. You want to do that during the cooler months.

That’s also the reason why you test your CYA level at the end of the season.

What chlorines to add when your pool cyanuric acid level is high?

If your pool CYA level is too high, it also means free chlorine in your pool won’t be effective. So you’ll have to add even more chlorine just to get to the normal free chlorine level.

In such a case, you wouldn’t want to add chlorine tablets or dichlor shock because those are both stabilized.

Instead, you want to add liquid chlorine or cal-hypo shock since those aren’t stabilized.

How to test cyanuric acid level in your pool

There are generally two ways to test for your cyanuric acid level. 

It’s a good idea to test your CYA level at the beginning and the end of each pool season.

You want to test at the beginning of the season, so if your CYA level is low, you can add more. 

You want to make sure your CYA level is optimal early on since your pool will use up more chlorine during the summer due to frequent swimming and the sunlight.

You’d also want to test at the end of the season to check if the level is too high. If your pool’s cyanuric acid level is too high, then it’s an indication you should change your pool water.

Since you’re only testing the cyanuric level of your pool every half a year or so, it’s a good idea to take your pool water to a reliable pool supply company and having them test the CYA level for you.

Just don’t let them into buying something you don’t need!

Best cyanuric acid test strips

Apart from getting your pool CYA level checked by professionals, you can also do it yourself using the cyanuric acid test strips.

I recommend you use aqua check pro if you decide to test your pool CYA level yourself. They test five things: total hardness, total chlorine, free chlorine, pH, and alkalinity.

Aquachek 7 is also a good option. This will test all five things mentioned above on top of cyanuric acid. Aquachek 7 will last you well over two years, so it’s a good investment.

How to use cyanuric acid test strips

Assuming you use Aquachek 7, if your CYA level is below 30, it is low. If it’s above 150, that’s considered high.

When you are using the test strips to determine your pool cyanuric acid level, you will simply dip your test strip into the pool and bring it out. Wait for about 15 seconds.

You’ll then check the color of the very bottom of your test strip and match it with the reading on your bottle to figure out the level of your pool CYA.

Is it safe to swim in a pool with high cyanuric acid?

A high cyanuric acid level doesn’t have any serious health implications, and it is not harmful in most cases.

But the problem is that a high pool CYA level reduces your chlorine’s effectiveness, which is essential for killing bacteria and viruses in your pool.

So while the CYA level does not directly affect your health, it can indirectly cause health problems due to a lower level of chlorine in your pool.

In short, it is not a good idea to swim in a pool with a high CYA level.

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