Swimming Pool Maintenance & High Cyanuric Acid Levels

Excessive cyanuric acid can lead to an unhealthy pool.
Excessive cyanuric acid can lead to an unhealthy pool. (Image: Adam Pretty/Lifesize/Getty Images)

Swimming pool maintenance can be a headache. No matter how hard you work to maintain optimum PH and chlorine levels, you may still face the irritating, and often mystifying, sight of cloudy or murky pool water. The culprit may be an excess of cyanuric acid – pool stabilizer – and you should address this before adjusting your water balance.

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Too Much Stabilizer

Sunlight has an adverse effect on water quality, dispelling chlorine and reducing pool sanitation. Cyanuric acid reduces the detrimental impact of ultraviolet light by forming a temporary bond with the free chlorine, the chlorine that is available to sanitize and oxidize the pool. Too much cyanuric acid locks the free chlorine, reducing its effectiveness and increasing the time it takes to kill harmful bacteria. Experts recommend maintaining cyanuric acid levels of 30 to 50 ppm.

Causes of Excess

Because cyanuric acid is a slow-dissolving product, many pool owners fall into the trap of retesting pool water and adding further stabilizer before the original dose has fully dissolved and circulated. This can result in excessive cyanuric acid concentrations. To avoid adding overdosing with stabilizer, do not retest your water for at least three days after adding the product. Adding stabilized chlorine products, such as Dichlor and Trichlor, in the form of tablets or powder, can also lead to excessive stabilizer concentrations. This is because the products contain both chlorine and cyanuric acid. Never use stabilized chlorine products shock or hyperchlorinate your pool.

Reducing Excess

Cyanuric acid is a stable product that does not diminish with pool use. Other pool treatments have no effect on its concentration; therefore excess stabilizer will not dissipate over time. To reduce cyanuric acid levels in your swimming pool, partially drain -- and then top up -- the water. Because this process will reduce the concentration of other pool chemicals, be sure to retest and make any necessary adjustments to the water balance.


Before buying chlorine products, check to see if they contain cyanuric acid and, unless you need to top up your stabilizer, select non-stabilized chlorine. Some suppliers market cyanuric acid stabilizer as “pool conditioner” – do not add this to the pool if your cyanuric acid level is within range. Always adhere to the manufacturers’ instructions when adding – or storing – pool chemicals.


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