Pool Care Pool Water Chemistry

Cyanuric Acid: When a Pool Needs It and How To Balance It

Swimming is a great way to relax and stay physically fit. Unfortunately, you have to add some chemicals to it to make it swimmable and safe. One of the many chemicals that go into a swimming pool is chlorine, which requires to be accompanied by things like Cyanuric Acid, also known as CYA.

This article will cover what Cyanuric Acid is, why it matters, and how you can use it to reduce chlorine loss and make your pool the perfect environment for you and your family to swim in without worrying about harsh chemicals or strong smells from chlorine!

What exactly is Cyanuric Acid?

Cyanuric Acid, or CYA for short, is a chemical found in your pool that acts as a stabilizer: it keeps chlorine from wearing off too quickly. Chlorine’s job is to kill bacteria and algae in the water.

When there isn’t enough chlorine or when it wears off completely, this can lead to an environment where organisms such as these thrive and make the water less clean and inviting for swimmers. The more cyanuric Acid present in your pool (in most cases), the longer your chlorine will last!

CYA is usually added at one of four levels based on recommendations by local authorities. This varies from country to country, but an average range would be somewhere between 20-50ppm.

According to the CDC (Center for Disease Control and Prevention), cyanuric acid levels should be tested weekly. Many people will test every few days or weekly, but testing it daily is not necessary unless you see algae starting to grow in the water!

Why Use Cyanuric Acid?

There are many benefits to having Cyanuric Acid in your pool. Cyanuric Acid inhibits UV rays from breaking down or deteriorating the chlorine that is currently in your pool.

If this happens, you will have to keep adding more chlorine, which can become very expensive over time – not to mention harmful for your skin.

It also helps control the pH levels of your pool because it “quadruples” how effective chlorine works. Now think about what could happen if you don’t use Cyanuric Acid.

Without it, you would need to constantly adjust your pool’s chemicals with test strips, which can take up an excessive amount of time and effort.

It even helps maintain a clean pool while protecting your pump and equipment from corrosion caused by chlorine.

So if you want to keep more money in your pocket, be able to enjoy a cleaner, safer swimming environment, and have less work to do daily, adding Cyanuric Acid might be the best decision you would ever make for your pool.

What does Cyanuric Acid Do?

Cyanuric Acid’s primary function is to protect chlorine from the sun – often called ‘the chlorine stabilizer.’ It acts as sunscreen for your chlorine. The UV radiation that passes through the water and into your pool evaporates the chlorine in your water, causing rapid breakdown. With the right amount of Cyanuric Acid in your pool, this process is slowed down, and chlorine can do its job better.

The more Cyanuric Acid in your pool, the longer it takes for chlorine to dissipate. At least 30 ppm of CYA should be maintained in highly chlorinated pools, while lower-chlorinated pools may get by less. The exception to this rule is if you have a saltwater pool or an SWG, you want no CYA because it inhibits the efficiency of your equipment.

Cyanuric Acid also prevents damage from free radicals when chlorine oxidizes contaminants in your water, including sweat, urine, and other organic materials.

Simply put: without CYA, these contaminants would oxidize your chlorine very quickly, rendering it useless.

In addition to keeping your chlorine from disappearing at record speed, Cyanuric Acid also prevents damage from free radicals, which cause scale and etching marks in plaster or vinyl liners. This is why a high level of CYA is important in pools with painted surfaces.

Cyanuric Acid has been linked to helping prevent Legionnaires ‘disease in public pools when the recommended levels are maintained. The recommended range for Legionella control is 30 – 50 ppm; most outbreaks of this disease have occurred outside that range.

How does Cyanuric Acid work?

Cyanuric Acid (or CYA) is a hexagonally shaped molecule that creates a monomeric ion in water. It can be said to work as an “extender” or an “enhancer” of chlorine’s performance at the end-user level, primarily by preventing the loss of those active chlorine atoms from exposure to sunlight and heat.

In short, it works almost like a part-time job for your pool chlorine. Cyanuric Acid is a big deal because it protects your chlorine investment by allowing you to use less – far less – chlorine than would otherwise be needed to generate equivalent levels of free available chlorine (FAC) with which to patrol the pool environment.

It works by bonding with free chlorine ions, thus slowing down their dissipation rate into the atmosphere. This action results in more active free chlorine ions being available to protect the pool for a longer period, making Cyanuric Acid an important component of any complete pool water treatment system.

Given this information, you might think that adding too much Cyanuric Acid to your pool would be good because it means you can stretch out how long your chlorine lasts and maintain proper sanitation for a longer period. Unfortunately, this is not the case.

You want as little Cyanuric Acid in your pool as possible. With too much Cyanuric acid present, a condition known as high total combined chlorine (chlorine plus Cyanuric Acid) can occur. High total combined chlorine levels will promote algae growth and cause odors and eye irritation problems to develop that are impossible to remedy without draining and refilling the pool with new water.

A level of 30 ppm of free chlorine is usually considered normal for a properly balanced pool. When this falls below 20 ppm, it usually indicates the need for additional chlorine or what is commonly called super-chlorination. It is recommended that all super chlorinators have Cyanuric acid or conditioner present, as this will help to prevent damage to the pool due to high pH.

What are the Cyanuric Acid Drawbacks?

1. Misleading Tests

Cyanuric Acid can fool oxidation-reduction potential (ORP), a measure of chlorine’s ability to sanitize a swimming pool effectively. ORP sensors come with probes that test the water conductivity in millivolts. They test free chlorine ions but not those attached to CYA.

When you add Cyanuric Acid to your pool, it reduces the ORP. That means if you add too much of the CYA, you can obliterate the sanitizer’s effectiveness, which would mean you wasted your valuable money to buy two chemicals that won’t help your pool clean and safe.

Once you add the right amount of CYA, you don’t have to top it up time and again. Cyanuric Acid tends to stay at the same level for a while. The only thing that can lower it is dilution when you top up the pool water or after a heavy storm.

2. Reduce Chlorine Effectiveness in Killing Chlorine-Resistant Microorganism

As I mentioned, at high CYA levels, pool chlorine is ineffective in killing microorganisms such as cryptosporidium parvum or crypto. It’s a chlorine-resistant microorganism responsible for gastrointestinal illness.

There are thousands of documented crypto cases in public pools each year, mostly related to fecal matter. If there is a suspected crypto case, the CDC (Centers for Disease Control and Prevention) recommends increasing the free chlorine concentration from 1-3 to 20 ppm for 32 hours. That is to inactivate around 99% of cryptosporidium inside the pool water.

However, this CDC recommendation doesn’t consider Cyanuric acid levels that might be in the swimming pool already. According to a recent CDC study, the current recommendation isn’t adequate to render the microorganism inactive even when the CYA levels are as low as 10-20 ppm.

It concludes by saying additional methods and other pool sanitation systems are required to protect the swimmers from such microorganisms.

What is the right Cyanuric Acid Level?

The ideal range for Cyanuric Acid (CYA) in a swimming pool is between 30-50 ppm. If the CYA level in your pool is below 30ppm, then you need to raise it. Anything higher than this can inhibit the sanitizer’s effectiveness in killing algae, bacteria, and other contaminants. At this level, you might start to see cloudy pool water, have a hard time keeping the pool chemistry balanced, and notice algae growth.

According to World Health Organization, the Cyanuric acid upper limit should be 100 parts per million. The limit is set with the assumption that young swimmers might swallow some of the treated water and, in the process, ingest the Acid, which can potentially make them sick if it’s higher.

You want to keep it around 50 ppm to enjoy its full benefits of protecting chlorine. If it goes above 100 ppm, your swimming pool will not be safe anymore, and you might not even get the readings on a test strip. The only way you can test it is by taking a sample of your pool water to a pool store for accurate testing so that you can know how low you need to go.

So, how can you lower Cyanuric acid levels?

Well! You will have to start by troubleshooting why you have more CYA in your pool. The best place to start is to check the type of chlorine you’re using.

You may have been using stabilized chlorine; the stabilization involves adding Cyanuric Acid to the sanitizer. That means, when you add some of the stabilized chlorine to your swimming pool, you’re adding some CYA too.

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What you want to look for on the chlorine you’re using is these chemicals:

  • trichloroisocyanurate
  • sodium dichloroisocyanurate
  • potassium dichloroisocyanurate

If your sanitizer package says it has either of these chemicals, then that is why you’re getting high CYA levels in your pool water. It’ll be best to switch to plain chlorine to prevent the levels from rising even more.

But that isn’t enough. You still need to reduce the amount of Cyanuric Acid in the pool to get the chlorine working normally again.

The best way to reduce the Cyanuric acid levels is to dilute the pool water with fresh untreated water. You can allow the water to splash out to lower the water level a bit and top it off with fresh water.

However, if the CYA levels as too high, the best option might be to drain the pool and refill it. Keep in mind that the Acid might hand around the pool filter. So, you will also have to backwash or change the cartridge when the levels are extremely high.

How to Add Cyanuric Acid to Your Pool

If you use stabilized chlorine such as Dichlor or Trichlor, you might not need to add more Cyanuric Acid to your swimming pool. As I mentioned earlier, the stabilizer is CYA, and whenever you add stabilizer chlorine, you’ll be adding some acid.

If you continue using the stabilized chlorine, the CYA levels with creep up over time, and you’ll need to lower it a bit. You can use unstabilized chlorine to avoid this problem and have the freedom of adding the right amount of Cyanuric Acid separately.

The good news is, when adding the CYA separately from the chlorine, you will only need to add it once or twice a year.

Keep in mind that Cyanuric Acid at high concentrations can damage the pool equipment, especially the filter or pool surfaces such as vinyl liner. And even though some labels direct that you add the Acid by pouring it directly into a filter or the pool water, avoid it.

Here’s the best and the safest way to add Cyanuric Acid to your pool:

Things you will need:

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  • Increases Cyanuric Acid Level
  • Decreases Chlorine Loss due to Sunlight

Step to Follow:

  • Step 1: Wear safety gear: acid-resistant gloves to protect the hands from acid burns and safety goggles to protect the eyes.
  • Step 2: Add warm water to the 5-gallon bucket to almost full.
  • Step 3: Follow the guidelines given in the product manual on the dosage. Measure Cyanuric Acid and add it to the warm water in the bucket. You need to add enough amount to reach 30-50 ppm. A rule of thumb is, you need 13 ounces of CYA to gain 10 ppm Cyanuric acid level in a 10,000-gallon pool.
  • Step 4: Using a clean stick, stir the content to ensure it’s well distributed in the warm water.
  • Step 5: Pour the bucket contents directly into the pool skimmer.
  • Step 6: Start the pool pump and run it for a few hours after to help stir the solution into the pool. If the package label says to add the Cyanuric Acid directly to the pool skimmer without adding it to some water is still okay. The manufacturer’s instructions always come first.

Related Questions

Do I need Cyanuric Acid when using Bromine as pool sanitizer?

No! Unlike chlorine, Bromine isn’t affected by sunlight. With the primary goal of adding CYA to reduce the effects of sunlight on chlorine, I don’t see the need to use it in your Bromine pool.

About the author

Sharif Miah

Hi! I'm Sharif, the founder of Globo Pool® and I have been working in the pool & hot tub industry for the last few years. I love to share my experiences with people & hope you are enjoying my information and lessons!

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