Cyanuric Acid – Why Use It and How Much?

You may or may not have heard about Cyanuric Acid and its effect on pool water. It is a necessary chemical to add to the water in most cases and proves indispensable in the fight against bacteria and algae. But, like most things, there can be too much of a good thing, and too much Cyanuric Acid (CYA in the pool business) actually cuts against our good fight and makes life more difficult.

Before we get to the downsides of CYA, let’s review briefly (very briefly, I promise) pool chemistry. As you know, our primary weapon against bacteria and algae is chlorine. Even if you have a salt pool, the water uses chlorine to fight off bacteria and algae. A vicious predator stalks chlorine though – UV rays. Chlorine is killed by UV and this negatively impacts chlorine’s ability to sanitize your pool water and oxidize the unwanted elements.

This is where CYA comes to the rescue. CYA protects chlorine from UV rays. It keeps chlorine around long enough to kill the bad stuff and oxidize it away. It binds itself to the chlorine molecule and enables chlorine to do its job. While protection and binding are good, they come at a price. You may have heard about “free chlorine” – this is chlorine unencumbered by UV and CYA and is the chlorine available for sanitization. Too much CYA in your pool and there won’t be enough free chlorine to properly sanitize your pool. Too little CYA and you will burn through your chlorine too quickly. The proper amount of CYA balances protection, binding, and sanitization ability.

But there is yet another consideration to CYA use. CYA stays in your pool water forever. There are some chemicals that claim to get rid of CYA, but they are very costly and create other issues for your pool water. Most experts recommend draining or diluting your pool water to get rid of excess CYA. Indeed, one publication says that draining/dilution is the “only practical” solution to too much CYA.

So, what is the proper amount of CYA? We prefer to keep CYA at 30 parts per million in your pool water. We can even work with water that has up to 50 ppm CYA in it. But above 50 ppm, we want to start altering our treatment plans. And once we get more than 70 ppm CYA in the pool, it is time to start considering draining your pool water and refilling it. Remember, draining your pool water and refilling is the most economical way of reducing the amount of CYA.

How do we get CYA into your pool? We either add it in granular form, or it gets added in automatically if you use pucks and a chlorinator to get chlorine into your pool. Unfortunately, we don’t manufacture pucks, and they come with CYA already in them. We can’t remove the CYA, nor can we control how much CYA comes with each puck. This is great if your pool water needs CYA, but detrimental if your pool is already high in CYA content. Once we get to 50 ppm point, we will need to supplement your chlorinator with liquid bleach (NOT household bleach) to keep the CYA in check.

CYA is a wonderful chemical to have in your pool. We just need to work together to keep the proper levels in your pool and treat the water if the level gets too high. Please call us if you have any pool questions and we’ll be happy to answer them.