What Is Pool Stabilizer?
What is pool stabilizer? Or maybe you are not familiar with that term and you know it as CYA, cyanuric acid, pool conditioner, water conditioner...these are all ways of talking about the same thing. Pool stabilizer is the chemical (cyanuric acid) that you add to your pool water to help your chlorine from burning off in the sun every day. This is the reason for the catchphrase often associated with pool stabilizer which is "CYA is like sunscreen for chlorine" and as far as a pool owner needs to understand it, this is a fairly accurate description.
Unstabilized chlorine will degrade in sunlight very readily. Any amount of chlorine that you have in your pool can be depleted by half for every hour that it is exposed to direct sunlight. This means that no matter how much chlorine you start your morning with, by the end of the day there will be no chlorine left in your pool. Enter a very helpful chemical, cyanuric acid, which does a fantastic job of letting the chlorine hang around for longer, even in prolonged exposure to direct sunlight. This is actually a massively important point, and is the main reason where there are not any real alternatives to chemical sanitizers like chlorine in swimming pools - ability to hold a sustained residual value in the water.
In order for us to consider water to be "safe" there must be four specific criteria that must be met by the protecting system. A failure to meet any one or more of these four criteria results in that system not being a viable option. In order to be safe the water must have a sanitizer, it must have an oxidizer, it must have an algicide, and finally, it must be able to hold a residual value. Many peripheral items like ozone systems or UV systems are amazingly effective at some of these criteria, however the lack of ability to hold a residual value in the water means these are not suitable as stand alone systems. They do not offer enough bather protection. Without a residual in the water, bacteria or parasites or any sort of harmful thing can live and grow (and contact swimmers) before it eventually finds its way through the filtration system many hours later. Every single alternative system you can name fails to meet the residual value component...but not chlorine. Not with the help of CYA as a stabilizer.
So the failure of mineral systems, UV lights, ozone systems, AOP and every other system you can name is the lack of residual protection in the pool water. But with the help of CYA chlorine is able to hold a residual, and this is the difference between safe water and decidedly less safe water. So now that we understand stabilizer is actually incredibly important in pools, and is the single chemical which facilitates this unique chlorine residual property that all other forms of disinfection fail to be able to achieve, we need to talk about the downside of CYA. CYA builds up in water and there is not any easy way to remove it from your water effectively. Any stabilized chlorine you add to your pool will add to the existing CYA levels. At 30 to 50 parts per million it helps greatly to hold your chlorine residual. At 80 to 100 parts per million that gentle hold turns into a crushing bear hug.
High Pool Stabilizer Levels - Since stabilizer, CYA, is hard to remove from pool water, if you are not mindful of the type of chlorine that you are using then you will eventually exceed the idea range of 30 to 50 parts per million. Once you reach 80 to 100 ppm the stabilizing effect of the CYA becomes too strong, and the chlorine is not able to sanitize bacteria and organic debris properly. At levels in excess of 100 parts per million chlorine levels need to be adjusted to account for this restriction from the CYA. This "chlorine lock" effect from high CYA either needs to be corrected by lowering the CYA through a partial drain and fill procedure, or the free chlorine levels must be increased in proportion to the CYA level.
The scope of the chemical interaction between CYA and chlorine goes well beyond that which the average pool owner needs to understand. It would however benefit you to know that CYA and chlorine is a hot button subject that gets discussed at the highest levels within the pool and spa industry, with scientists, people who make up the rules governing operation of aquatic facilities, the aquatic facilities themselves...if you wear a lab coat to work then you might enjoy reading about "The Great CYA Debate" which has literally been a contention point for decades within the industry. If you are a pool owner who just wants to go swimming then keep your CYA levels in the 30 to 50 range and when you reach 80 it is time to do a partial drain and fill for your pool.
If you would prefer not to partially drain your pool then you should be aware of which chlorine form you use to shock and maintain your chlorine levels. There are many choices available to pool owners for chlorine that will not increase your CYA levels. In many cases it is above ground pool owners who jumped into pool ownership perhaps with a little less overall planning and research. These are the pool owners with green water who come into a water lab for the first time and they have a CYA level of 200 and basically zero chance of clear water without intervention. Instead of using regular dichlor or trichlor tablets in a floater consider using cal hypo, liquid chlorine, chlorine from salt water or lithium hypochlorite, but be sure to NEVER mix and match chlorine in any device like a floater or erosion feeder. Mixing chlorine can cause a chemical explosion!
If you are stuck with high CYA levels because you do not have the option to drain your pool for one reason or another, then you can read more about how to work with high(er) CYA levels. In short you will need to increase your free chlorine level to 5% or up to 7.5% of the CYA level in your pool, depending on who you ask. So a CYA level of 100 would need between 5 ppm and 7.5 ppm of free chlorine in order to be active enough to keep green water and bacteria at bay. At CYA levels of 150 ppm you would need 7.5 to 11.25 ppm of free chlorine in the water. As you can see CYA has quite a strong relationship with chlorine and the function of chlorine in your pool water.
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