Swimming Pool Blog
by Rob Cox, October 17, 2012
Cyanuric Acid: aka Conditioner or Stabilizer
Cyanuric Acid, or C³H³N³0³, belongs to the chemical family of Isocyanurates, and is used as a chlorine stabilizer. It forms a weak bond with chlorine, and shields the molecule from degradation by the sun's ultra-violet rays.
Cyanuric acid is abbreviated as CYA, and is commonly sold in granular form, and may be labeled as pool "conditioner" or "stabilizer".
Who should use Cyanuric Acid?
Outdoor swimming pools can benefit the most from having a proper level of Cyanuric acid in the pool water, by protecting the chlorine from rapid depletion by the sun. In the parlance of chemical additives, Cyanuric acid is considered a "stabilizer", as it stabilizes the chlorine molecule from solar degradation.
Indoor pools and spas or hot tubs need not use Cyanuric Acid, since the exposure to sun in both cases is usually very minimal.
What Level of Cyanuric Acid is Optimum?
Even very small amounts of Cyanuric acid will help extend your chlorine lifespan in an outdoor pool. CYA is measured in parts per million, and a reading of 30 - 50 ppm is considered optimum. Some experts will claim that it should be closer to 30 ppm, while others support a different range of 40-80 ppm.
All experts agree however, that when Cyanuric acid levels are too high, a phenomenon known as "Chlorine Lock" can occur, where your test kit will show no chlorine in the water, even though you have witnessed chlorine tablets dissolving, or have just shocked the pool. Generally, this occurs when CYA levels climb close to 100 ppm.
Cyanuric acid levels should be maintained above 30 ppm and below 80 ppm. The higher your level of Cyanuric acid is, the less efficacy, or killing power your chlorine has. At CYA levels approaching 100 ppm, you will have superior protection from the sun, but your chlorine molecule becomes weaker due to the amount of CYA attachments or bonds being made.
A 2007 study by the CDC showed that levels of Cyanuric acid above 50 ppm significantly diminished chlorine’s ability to kill bacteria. Chlorine molecules that are "over-protected" by too much CYA can lead to excess chloramine formation, as nitogen and ammonia are easily able to attach themselves to these "slow and sluggish" chlorine molecules.
What is Stabilized Chlorine?
Certain types of chlorine products are labeled "Stabilized", namely Trichlor tablets and Dichlor shock. These two products are in the family of isocyanurates, and put simply - they already have Cyanuric acid in the mix. Using Trichlor tablets, as most people do, you can expect the tablets to add a small amount of Cyanuric acid to the water. Over time, adding these small amounts of CYA to your pool may cause your Cyanuric acid level to rise to high.
In most cases, however, using Trichlor tablets or Dichlor shock won't cause your CYA level to climb very noticeably, especially if you replace water regularly through backwashing or winterizing. And, in most cases, you will need to add pool stabilizer or conditioner to your pool to raise the level to where you can notice the difference.
How do I Raise Cyanuric Acid Levels in my Pool?
By adding pool Conditioner or Stabilizer directly to the pool. Follow the container directions, some manufacturers may suggest diluting the powder in a bucket of water and then adding, while some will suggest that you broadcast it over the pool surface. Some may suggest that you add it into the skimmer, although I would only do this for sand filters (not DE or Cartridge).
Adding the correct amount of Cyanuric acid is important, so that you don't overshoot the mark. Make sure that your CYA level is tested, and you know your pool size, in gallons - to determine the correct amount of Cyanuric acid to add to the pool. If you have drained your pool and are refilling, you will likely be starting from zero, however - some water treatment facilities use Cyanuric acid in their process. Again, be sure to test your water first, and be careful to add the proper amount to the pool.
How much Cyanuric Acid do I add to my Pool?
Check the label for correct dosages, but to help you buy enough to do the job, here's a quick formula. Buy 4lbs of Cyanuric acid per 10,000 gallons of pool water, to raise the CYA level by 30-40ppm. For example, when refilling a 25,000 gal pool, you need 10 lbs of granular Cyanuric acid. Test your CYA levels every few months. Over time, you will likely need to add booster treatments to maintain the residual. A few pounds per year is common, but be sure to test your CYA levels first, and not add more blindly.
How do I Lower Cyanuric Acid levels in my Pool?
By dilution, which means to drain a portion of pool water and refill with water that has no, or very low levels of Cyanuric acid. There is no chemical available that will remove Cyanuric acid, and it does not deplete on its own. It will be reduced by dilution from rain, backwashing, splashout and lowering the water level for winter. If you drain out 20% of your pool, refill the pool, voila! your CYA level will be reduced by 20%.
How do I Test the Water for Cyanuric Acid?
With a Test Kit for Cyanuric acid, of course! This test is usually the last test to be included on pool test kits, meaning that you only find it standard on the better test kits and test strips. The Pro II test strips, shown right however, test for Total Dissolved Solids (TDS), Cyanuric Acid (CYA) and Total Hardness levels in your pool. $12 for 25 tests.
If you have a local pool supply store, most will offer free water testing, just bring them a pool water sample during business hours.
Is Cyanuric Acid Dangerous or Unhealthy?
Cyanuric Acid, by itself is not immediately dangerous or hazardous to one's health. It can cause eye or skin irritation if direct contact is made. It is not toxic or carcinogenic. Based on data from toxicological investigations, Cyanuric acid does not damage organs. Damage to the kidneys and bladder has been observed in rats tested with a saturated solution (5375 ppm) of Cyanuric acid for their drinking water. CYA should not pose a risk to humans during manufacture, use in swimming pools, or even by ingesting diluted solutions of Cyanuric acid. Cyanuric acid is quickly excreted unchanged from the kidneys.
Can I use Cyanuric Acid to Lower my pH?
Technically, CYA is an acid, and is in the family of Sulfuric acid - with a pH level of around 4.0. It will slightly reduce your pH level when added to the pool in measureable quantities, but may be hard to notice. So, no - Cyanuric acid is best used for shielding your expensive chlorine from the sun - but for lowering your pH, better to use Sodium Bisulfate.