Full Guide: Cyanuric Acid & Why Is It Vital for Pools

If you’ve decided to research cyanuric acid, I can already be proud of you — not every pool owner is interested in it. It may seem complicated, incomprehensible, and even unnecessary, but trust me, knowing about pool chemicals is vital if you want it always to be up and running.

Today I’m going to tell you the basics you need to know about cyanuric acid. What it is, why it’s significant for the pool, how to raise or lower your CYA levels, and more. Stay tuned if you’re ready for some new info.

What is cyanuric acid?

Cyanuric acid is a stabilizer and protection for chlorine from direct sunlight in the pool. What’s wrong with the sun? Well, straight sunlight can destroy chlorine in a matter of hours and it is not what we are striving for. Chlorine is essential because it performs three basic tasks to keep your pool clean it:

• Disinfects (kills bacteria and germs);
• Oxidizes (controls organic debris from sweat and grease deposits)
• Keeps algae away.

Cyanuric acid is also known as isocyanuric acid, CYA, pool chlorine stabilizer, or chlorine conditioner and protector. And now we’re going to get into the maze of chemistry a little bit.

Why do you need it for your pool?

The balance of free chlorine and cyanuric acid is very critical. Lack of stabilizer in outdoor pool water leads to the destruction of chlorine by UV radiation. Excess stabilizer partially or completely blocks chlorine. Both the first and the second situation leads to the overuse of chlorine. For rational use of chlorine, stabilizer and chlorine are used separately, with constant control of the stabilizer by express testers. Cyanuric acid allows the chlorine added to the pool to last longer without being exposed to sunlight. 

To show you the real difference, here are the numbers:

Pros

• At 10 ppm CYA, 87% of the chlorine will be left in an hour.
• At 30 ppm CYA, 98% of the chlorine will be left in an hour.

Cons

• Without cyanuric acid, the half-life of chlorine in an outdoor pool would be 45 minutes.
• Over the next 90 minutes, another half of the chlorine will be gone.

What should be the CYA level in the pool

To achieve the ideal levels in the pool water, various chemicals must be added in a certain balance and constantly monitored. Contrary to popular belief, these chemicals are not harmful to human health when used in pool water. In fact, keeping it in the right amount prevents the destruction of various microorganisms resulting from the use and the spread of elements that threaten human health, such as bacteria and viruses.

For cyanuric acid to work properly, its concentration should be within 30-50 mg per liter of water. Otherwise, the chlorine will not be able to effectively cope with its tasks. That is why the appearance of algae in a bowl with a high level of chlorine is, first of all, to measure the concentration of this stabilizer.

How to measure CYA

You need to remember that the level of cyanuric acid in the pool should always be normal. The only exception is when there are heavy rains, a lot of fresh water can get into your pool and the CIA level will drop. Then test the water and add cyanuric acid as needed. There are several ways to measure cyanuric acid in the pool.

The easiest option is to use test strips. You can usually find them in a pool water test kit. You dip the desired strip into the water for a few seconds, then wait a while for the water to react with the reagents on the strip. Finally, you simply compare the color of your strip to the one pictured on the package. Of course, this whole process is even more detailed in the instructions. 

Another testing option is turbidity tests, with which you have to do a little bit of fiddling but they are very accurate if you do it right. You need to order a special kit, which usually consists of a glass test tube, a plastic vessel, and chemical reagents (different manufacturers may add a wand or pipette at their discretion, etc.)

The main thing is to have a black dot or stripe on the bottom of the glass test tube. The whole process is usually described in detail in the instructions, but we will explain the gist to you. You will draw water into the plastic test tube. Next, you add a chemical reagent. If you don’t have a spoon in the kit, you can use your own (glass or plastic). The next step is to wait for the reagents to react. 

How do you evaluate the result? The murkier the water, the more cyanuric acid it contains.

However, this is not the end of the test. 

Next, you must transfer the obtained solution into a glass test tube (do not overfill!). This should be done using a pipette. And you should put the glass test tube in a well-lit place and look at it from above to see a black dot or line. Pour one drop of the solution until you can no longer see the black dot (line). Now check the water level in the test tube. There will be a graduated line that will show the exact level of cyanuric acid concentration in your pool.

How to use cyanuric acid properly

Too high or too low a CYA level in the pool is bad, but not fatal. Either case can be corrected. 

How to raise

If you need to increase your cyanuric acid levels, use a pool stabilizer. This is a product that stabilizes free chlorine in the pool from evaporating in the sun. 

Where do you get it? It is sold as a stand-alone product or directly with chlorine in liquid or pellets. If you buy two-in-one, your pool’s CYA levels will go up automatically. Sometimes it may not be enough (or too much) — in such cases it is convenient to use a separate product to balance the cyanuric acid. You can determine this by doing some water tests before and after adding chlorine and CYA.

How to lower

Reminder, if you have too much cyanuric acid in your pool, the chlorine loses its effectiveness and can’t clean the water as it should. How do you fix this? There are two common ways.

The first is to partially drain the pool. For example, if you have 15% too much CYA, drain about 15% of the pool and replace it with regular fresh water. Turn on the pump to agitate the water, then do a new check of the chemical levels. If the cyanuric acid level is still high, repeat the procedure. This is the safest and simplest way to reduce CYA, so don’t hesitate to try it.

The second option is to buy a reverse osmosis (RO) filter. This is a special filter that helps trap CYA and remove it from the water. This is a more expensive option but less time and effort-consuming, especially if you can’t or don’t want to drain the water and pour in new water.

There are also special products — CYA reducers — which can also solve this problem, but they work slower.

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

First, since there is no connection between cyanuric acid and cyanide, it is suitable for use in swimming pools from a health perspective. If the level of cyanuric acid in your pool is within normal limits, you can fear nothing and safely swim in it. We only recommend waiting half an hour after adding cyanuric acid (as with other chemicals) before getting in the pool to let it completely dissolve in the water.

Now let’s look at options outside the norm. If the CYA level is below normal, the pool may become dangerous from a hygiene point of view. As you remember, chlorine is destroyed by the sun if there is not enough cyanuric acid in the water, and therefore cannot clean the water as effectively as before.

However, as cyanuric acid levels increase, the effectiveness of chlorine also decreases. To avoid being affected by this negativity, you should monitor developments closely and test your water regularly.

Summary

So, we sincerely hope that you now have a general (or even a clear) understanding of cyanuric acid and its importance to the pool. Without it, the chlorine will not work properly and thus you are taking a big risk if you dare to swim in your pool. 

So check the CYA level at least once a week (and after the rains), add or partially drain the pool water if necessary, and you’ll be happy. Or at least you will have safe clean water in the pool, and that’s something.

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