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What is Cyanuric Acid?

The purpose of CYA is not to make you sound smart when you casually toss it out in conversation. In an outdoor pool (indoor pools typically do not require any CYA) with no CYA, chlorine is consumed within the first 2 hours of sunlight hitting the pool.  CYA serves to protect the chlorine and allow it to stick around longer.  However, too much CYA will bind over the chlorine and will not allow it out to work.  We often hear that “My pool is in chlorine lock or it won’t hold it” when it really is present but unable to break through the higher levels of CYA that are present in your water chemistry. In the end, there is a direct relationship to the amount of CYA in a pool and the proper chlorine level. The multiplier to figure out how much chlorine (in ppm) you need is .075.   In the case of a pool with 30 ppm CYA, we would take 30 times .075 to get minimum chlorine residual of 2.25 ppm (we always talk about free chlorine here because it combats algae).  A pool with 100 ppm then would require a minimum of 7.5 ppm free chlorine as 100 X .075 = 7.5.  Oftentimes in our industry, we hear that 2-4 ppm free chlorine is good, with no regard to the relationship it has with CYA.  With this simple example, you can see that a pool with 100 ppm or higher as we see a fair amount because of the popularity of chlorine tabs, CYA and only a 4 ppm free chlorine residual is asking for….. ALGAE!  You must either lower your CYA level or increase your free chlorine to keep a safe and sanitary pool in this case. This is challenging because if you’re dealing with higher levels of CYA in the summertime having to have higher levels of free chlorine can be tough.

How To Remove CYA From Your Swimming Pool

In the swimming pool industry, they commonly recommend a drain and refill but at Pure Water Industries we believe the simplest way to lower CYA in your swimming pool is using Reverse Osmosis (RO) filtration or what we like to call “Puripool.” We regularly see swimming pools with high levels of CYA and RO filtration can and will lower it. We recently recycled a residential swimming pool with CYA levels of over 200 ppm which means free chlorine would have to be at 15 ppm or higher to combat algae. This is a problem……

Initial Chemistry

Calcium Hardness – 540 ppm

Total Dissolved Solids – 2208 ppm

Cyanuric Acid – 200+ ppm

After filtering this swimming pool we were able to lower CYA to much better levels.

Ending Chemistry

Calcium Hardness – 120 ppm

Total Dissolved Solids -324 ppm

Cyanuric Acid – 25 ppm

Reverse Osmosis if the best solution for high levels of CYA in your swimming pool because it not only conserves up to 85% of the water in the swimming pool but it also lowers Calcium Hardness, TDS, and so much more. To learn more about RO and how it can help you, please contact us today!