AQUATIC FACILITY OPERATOR (AFO) PRACTICE
EXAM 70 Questions Correct Answers Clear
Rationales
1. The ideal pH range for pool water is:
Answer: 7.2–7.8
Rationale: Ensures disinfectant efficiency and swimmer comfort.
2. The most effective pH for chlorine disinfection is around:
Answer: 7.2
Rationale: Hypochlorous acid (HOCl) concentration is highest around
7.2.
3. Free chlorine should be maintained at:
Answer: 1–4 ppm
Rationale: AFO and CDC MAHC guidelines for safe, effective sanitizing.
4. Combined chlorine should not exceed:
Answer: 0.2 ppm
Rationale: Higher levels indicate chloramines, which require shocking.
5. Breakpoint chlorination requires:
, Answer: 10 times the combined chlorine level
Rationale: “10x rule” oxidizes chloramines.
6. Total alkalinity ideal range:
Answer: 80–120 ppm
Rationale: Helps buffer pH, preventing rapid changes.
7. Calcium hardness ideal range for plaster pools:
Answer: 200–400 ppm
Rationale: Prevents etching (low CH) or scale (high CH).
8. The Langelier Saturation Index (LSI) helps determine:
Answer: Corrosive or scale-forming water
Rationale: Balances pH, CH, TA, temperature, TDS.
9. What form of chlorine is most effective at low pH?
Answer: Hypochlorous acid (HOCl)
Rationale: Active disinfectant.
10. The main drain’s purpose includes:
Answer: Circulation and removal of deep-water debris
11. Anti-entrapment compliance requires:
EXAM 70 Questions Correct Answers Clear
Rationales
1. The ideal pH range for pool water is:
Answer: 7.2–7.8
Rationale: Ensures disinfectant efficiency and swimmer comfort.
2. The most effective pH for chlorine disinfection is around:
Answer: 7.2
Rationale: Hypochlorous acid (HOCl) concentration is highest around
7.2.
3. Free chlorine should be maintained at:
Answer: 1–4 ppm
Rationale: AFO and CDC MAHC guidelines for safe, effective sanitizing.
4. Combined chlorine should not exceed:
Answer: 0.2 ppm
Rationale: Higher levels indicate chloramines, which require shocking.
5. Breakpoint chlorination requires:
, Answer: 10 times the combined chlorine level
Rationale: “10x rule” oxidizes chloramines.
6. Total alkalinity ideal range:
Answer: 80–120 ppm
Rationale: Helps buffer pH, preventing rapid changes.
7. Calcium hardness ideal range for plaster pools:
Answer: 200–400 ppm
Rationale: Prevents etching (low CH) or scale (high CH).
8. The Langelier Saturation Index (LSI) helps determine:
Answer: Corrosive or scale-forming water
Rationale: Balances pH, CH, TA, temperature, TDS.
9. What form of chlorine is most effective at low pH?
Answer: Hypochlorous acid (HOCl)
Rationale: Active disinfectant.
10. The main drain’s purpose includes:
Answer: Circulation and removal of deep-water debris
11. Anti-entrapment compliance requires:
