NASCO Facility Operations & Maintenance 5 — Questions and Answers
Question 1: When should a pool operator perform a water chemistry test at minimum during high-use periods?
- Once per week
- Every 4 hours or before each operational period (Correct answer)
- Only when the water appears cloudy
- Once daily at closing
Correct answer: Every 4 hours or before each operational period
During high-use periods, most health codes and NASCO guidelines require testing at least every 4 hours to ensure chemical levels remain within safe ranges.
Question 2: A pool has a combined chlorine reading of 0.6 ppm and a free chlorine reading of 1.2 ppm. What is the total chlorine?
- 0.6 ppm
- 1.2 ppm
- 1.8 ppm (Correct answer)
- 0.4 ppm
Correct answer: 1.8 ppm
Total chlorine equals free chlorine plus combined chlorine: 1.2 + 0.6 = 1.8 ppm.
Question 3: What is the primary regulatory purpose of a pool log or water chemistry record?
- Marketing the facility's cleanliness to the public
- Providing documentation of compliance and enabling trend analysis (Correct answer)
- Tracking swimmer attendance only
- Recording lifeguard rotation schedules
Correct answer: Providing documentation of compliance and enabling trend analysis
Chemical logs provide a compliance record for health inspectors and allow operators to identify trends such as recurring pH drift or chlorine demand spikes.
Question 4: Which condition would cause a DPD test kit to give a 'bleached out' (false low) chlorine reading?
- Low pH in the sample
- Very high chlorine levels above 10 ppm (Correct answer)
- High total alkalinity
- Low water temperature
Correct answer: Very high chlorine levels above 10 ppm
At very high chlorine concentrations, excess oxidizer bleaches the DPD indicator back to colorless, producing a falsely low or zero reading — this is called the 'fade out' effect.
Question 5: What minimum depth of water must be present at the point of entry for a head-first dive to be considered safe according to aquatic safety standards?
- 4 feet
- 5 feet
- 9 feet (Correct answer)
- 6 feet
Correct answer: 9 feet
NASCO and most aquatic standards require a minimum of 9 feet of water depth in the diving envelope for safe head-first entry from a 1-meter springboard.
Question 6: What is the recommended calcium hardness range for swimming pool water?
- 50–100 ppm
- 200–400 ppm (Correct answer)
- 500–700 ppm
- 10–50 ppm
Correct answer: 200–400 ppm
Calcium hardness of 200–400 ppm prevents water from being corrosive to plaster and metal surfaces or from depositing scale on pool equipment.
Question 7: Under NASCO guidelines, which situation requires a pool to be closed immediately for remediation?
- pH reading of 7.8
- Free chlorine at 2.5 ppm
- Fecal contamination incident in the pool (Correct answer)
- Turbidity slightly above normal
Correct answer: Fecal contamination incident in the pool
A fecal contamination incident requires immediate pool closure, hyperchlorination to appropriate CT values, and clearance testing before reopening to prevent disease transmission.
NASCO Facility Operations & Maintenance 5
When should a pool operator perform a water chemistry test at minimum during high-use periods?