Cyanuric acid, or CYA, is an important substance that helps stabilize chlorine in a swimming pool by preventing it from being destroyed by the sun’s UV rays. When chlorine is destroyed, the pool water becomes susceptible to harmful pathogens and germs.

However, it takes a lot of watchful care to ensure that CYA and the chlorine it protects are kept in balance. Increasing levels of CYA also slows chlorine’s ability to destroy germs quickly, causing the water quality to become questionable, and also increases risk of algae blooms.

“When you add cyanuric acid to the water, it's going to slow down the kill rate,” says Ellen Meyer, product safety and government affairs manager at Solenis. “The more you slow down the kill rate of these organisms, then the higher your risk of actually getting ill from the organisms. Because germs are going to last longer in the pool when cyanuric acid is present, you are more likely to swallow them and then become ill from them.”

Meyer says it’s a balancing act – making sure there’s enough active chlorine in the pool to effectively kill those organisms. Ideally the minimum amount of cyanuric acid needed to maintain a chlorine residual should be used. This may be as high as 30 to 50 parts per million of cyanuric acid. At the same time, the ratio of CYA to chlorine is also critical: chlorine should be at least 7.5 percent of cyanuric acid levels, and free chlorine levels should be at about 1-4 ppm.

Cyanuric acid is usually introduced at the beginning of the swim season, when the pool is opened. Meyer says that should be the only time it’s added, since it does not dissipate the way chlorine does. The only way to remove CYA is by removing water, sometimes through splash-out, or backwashing. For that reason, it’s critical to make sure not to over-add it, or the pool will need to be drained to balance the chemicals.

Those who use trichlor-s-triazinetrione tablets, or trichlor for short, can benefit from having both chlorine and CYA in it and slowly released into the water. However, the issue still remains in that it can cause less effective chlorine performance, as well as build-up of CYA that would eventually need to be drained out if it gets too high.

According to Meyer, a non-stabilized tablet, or NST, is the most effective product for sanitizing a pool. They are made up of mostly calcium hypochlorite, or cal hypo, with no CYA. NST is designed to be slow-dissolving and slow-releasing, easily placed in a pool feeder, floater or skimmer, and actively killing organisms. Pool owners only need to replace the tablets on a regular basis, such as weekly, as long as they continue to test the water to ensure 1-4ppm chlorine residual.

Meyer touts the advantages of the NST. “It's really low tech, so you don't need a lot of fancy equipment then to feed your chlorine into the pool. It's a really simple feeder, or you can put the tab in the skimmer and it'll slowly dissolve in the skimmer and then go out into the pool. So it's an easy way to maintain a residual over an extended period of time.”

The result is a sparkling, clean, sanitized, chlorinated swimming pool that, if monitored regularly, is easy to maintain, and even easier to enjoy!

For more information, visit Solenis.