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Chemical Reduction of Cyanuric Acid in Swimming Pools Using Aluminum Sulfate
– from the published research and field methods of Rudy Stankowitz, with independent confirmations from Service Industry News, PoolSharkH2O, and AQUA Magazine.

Background

Cyanuric Acid (CYA) is an essential stabilizer in outdoor pools, protecting chlorine from rapid UV degradation. However, excess CYA (>100 ppm) compromises sanitizer efficiency, leading to cloudy water, algae growth, and regulatory compliance challenges. Traditionally, the only remedy was partial or full draining and dilution—an expensive, wasteful, and sometimes impractical solution.

In 2019, Rudy Stankowitz introduced and field-tested a novel chemical method for lowering CYA by using aluminum sulfate (alum). The process leverages the formation of insoluble aluminum–cyanurate complexes, which can be flocculated and removed from the pool. Since then, the method has been peer-published, refined, and independently validated.

Chemistry of the Process

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  Reaction Basis: Aluminum ions (Al³⁺) introduced via alum dosing react with cyanurate anions, forming insoluble aluminum cyanurate complexes.

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  Key Difference from Standard Floc: Unlike conventional alum use (which targets turbidity and organics), this reaction is specific to complexing CYA molecules.

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  Outcome: A measurable reduction of CYA levels—typically 25–50% per treatment cycle under controlled conditions.

Standard Field Protocol (R. Stankowitz, 2019–2024)

1. Pre-conditions:

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     Water temperature ≥ 70 °F (21 °C)

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     pH adjusted to ~7.0

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     Total Alkalinity in 80–100 ppm range

     
     
2. 
   

   Dose Rate: 8.33 lb (3.78 kg) alum per 10,000 gallons (37.8 m³)

3. Application:

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     Broadcast evenly across pool surface

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     Circulate for short duration (typically 1–2 hours)

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     Shut down circulation to allow settling (12–24 hours)

4. Removal:

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     Vacuum flocculated material to waste

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     Resume filtration and adjust water balance as needed

This method does not rely on granular chlorine or secondary oxidizers during treatment.

Independent Validations

Service Industry News (March 31, 2024)

In controlled field trials, Que Hales reported a ~25% CYA reduction per treatment cycle using Rudy’s alum-based method. These results confirm the reproducibility of the process outside of its originator’s field studies.
Source: Service Industry News (serviceindustrynews.net)

PoolSharkH2O Blog (April 17, 2023)

An industry-facing technical summary credited Rudy with the innovation and highlighted the critical sensitivity to pH and temperature. The blog emphasized that deviating from the recommended chemistry conditions led to inconsistent outcomes, reinforcing the importance of following the detailed procedure.
Source: PoolSharkH2O Blog (blog.poolsharkh2o.com)

AQUA Magazine (October 9, 2024)

In an editorial profile, AQUA Magazine documented Rudy’s development of the alum-based chemical reduction method and noted its subsequent validation by independent sources in 2024. This positioned the method as a game-changing alternative to draining in the pool industry.
Source: AQUA Magazine (aquamagazine.com)

Reported Outcomes

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  CYA Reduction Range: 25–50% per treatment cycle depending on adherence to conditions.

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  Secondary Benefits: Simultaneous phosphate removal (since alum also binds phosphates), and improved water clarity.

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  Operational Impact: Provides pool operators with a cost-effective, water-conserving option to manage stabilizer levels.

Industry Significance

This method represents the first widely-documented chemical protocol for direct CYA reduction in situ. By avoiding costly drain/refill cycles, it reduces water waste, minimizes downtime, and offers commercial aquatic facilities a practical compliance pathway.

The method has now moved from experimental innovation (2019) → technical validation (2020–2023) → independent confirmation and industry adoption (2024).

Reference

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