CPO Pool Water Chemistry 3 — Questions and Answers
Question 1: Breakpoint chlorination requires adding free chlorine at approximately how many times the combined chlorine level?
- 3 times
- 5 times
- 7.6 times (Correct answer)
- 15 times
Correct answer: 7.6 times
Breakpoint chlorination requires adding roughly 7.6 times the combined chlorine level to destroy chloramines and reach breakpoint.
Question 2: Combined chlorine (chloramines) forms when free chlorine reacts with:
- Calcium compounds
- Nitrogen-containing compounds such as ammonia and urea (Correct answer)
- Carbon dioxide dissolved in water
- Cyanuric acid
Correct 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.
Question 3: What is the maximum recommended combined chlorine level in pool water per NSPF CPO standards?
- 0.1 ppm
- 0.2 ppm (Correct answer)
- 0.5 ppm
- 1.0 ppm
Correct answer: 0.2 ppm
Combined chlorine should not exceed 0.2 ppm; higher levels indicate chloramine buildup causing odor and eye irritation.
Question 4: Cyanuric acid (conditioner/stabilizer) protects free chlorine from destruction by:
- UV sunlight (Correct answer)
- Heat from pool heaters
- pH fluctuations
- Bather-introduced bacteria
Correct answer: UV sunlight
Cyanuric acid forms a reversible bond with chlorine, shielding it from photodegradation by UV rays in sunlight.
Question 5: What is the recommended cyanuric acid range for outdoor chlorinated pools?
- 0–10 ppm
- 10–40 ppm (Correct answer)
- 50–80 ppm
- 100–150 ppm
Correct answer: 10–40 ppm
The CPO-recommended cyanuric acid range is 10–40 ppm; exceeding 100 ppm can over-stabilize chlorine and reduce disinfection.
Question 6: Which sanitizer types are naturally stabilized because they contain cyanuric acid in their formulation?
- Calcium hypochlorite and sodium hypochlorite
- Chlorine gas and sodium hypochlorite
- Trichlor and dichlor (Correct answer)
- Bromine and calcium hypochlorite
Correct answer: Trichlor and dichlor
Trichlor (trichloroisocyanuric acid) and dichlor (sodium dichloroisocyanurate) are chlorine compounds that contain bound cyanuric acid.
Question 7: Total chlorine in pool water is calculated as:
- Free chlorine minus combined chlorine
- Free chlorine plus combined chlorine (Correct answer)
- Combined chlorine divided by free chlorine
- Free chlorine only, combined is not counted
Correct answer: Free chlorine plus combined chlorine
Total chlorine = free chlorine + combined chlorine; a DPD test measures total, and subtracting free chlorine gives combined chlorine.
CPO Pool Water Chemistry 3
Breakpoint chlorination requires adding free chlorine at approximately how many times the combined chlorine level?