Pool Water Chemistry Flashcards

Breakpoint chlorination requires adding free chlorine at approximately how many times the combined chlorine level?

Answer: 7.6 times

Breakpoint chlorination requires adding roughly 7.6 times the combined chlorine level to destroy chloramines and reach breakpoint.

Combined chlorine (chloramines) forms when free chlorine reacts with:

Answer: Nitrogen-containing compounds such as ammonia and urea

Chloramines form when free chlorine combines with ammonia and urea from sweat, urine, and body oils introduced by bathers.

What is the maximum recommended combined chlorine level in pool water per NSPF CPO standards?

Answer: 0.2 ppm

Combined chlorine should not exceed 0.2 ppm; higher levels indicate chloramine buildup causing odor and eye irritation.

Cyanuric acid (conditioner/stabilizer) protects free chlorine from destruction by:

Answer: UV sunlight

Cyanuric acid forms a reversible bond with chlorine, shielding it from photodegradation by UV rays in sunlight.

What is the recommended cyanuric acid range for outdoor chlorinated pools?

Answer: 10–40 ppm

The CPO-recommended cyanuric acid range is 10–40 ppm; exceeding 100 ppm can over-stabilize chlorine and reduce disinfection.

Which sanitizer types are naturally stabilized because they contain cyanuric acid in their formulation?

Answer: Trichlor and dichlor

Trichlor (trichloroisocyanuric acid) and dichlor (sodium dichloroisocyanurate) are chlorine compounds that contain bound cyanuric acid.

Total chlorine in pool water is calculated as:

Answer: Free chlorine plus combined chlorine

Total chlorine = free chlorine + combined chlorine; a DPD test measures total, and subtracting free chlorine gives combined chlorine.