NASCO Facility Operations & Maintenance 2 — Questions and Answers
Question 1: What is the recommended free chlorine residual range for a public swimming pool in most US states?
- 0.5–1.0 ppm
- 1.0–3.0 ppm (Correct answer)
- 3.5–5.0 ppm
- 5.0–7.0 ppm
Correct answer: 1.0–3.0 ppm
Most US health codes require free chlorine between 1.0 and 3.0 ppm to ensure effective disinfection without causing irritation.
Question 2: Which piece of equipment is primarily responsible for removing suspended particles from pool water?
- Chemical feeder
- Circulation pump
- Sand or DE filter (Correct answer)
- UV disinfection unit
Correct answer: Sand or DE filter
Sand, diatomaceous earth (DE), and cartridge filters physically trap suspended particles to clarify pool water.
Question 3: A pool operator notices foamy water on the pool surface. What is the most likely cause?
- Excessive cyanuric acid
- High total dissolved solids (TDS)
- Body oils, lotions, or soaps introduced by swimmers (Correct answer)
- Low calcium hardness
Correct answer: Body oils, lotions, or soaps introduced by swimmers
Foamy water is typically caused by organic contaminants such as body oils, sunscreen, and soaps introduced by bathers.
Question 4: What is the primary purpose of backwashing a sand filter?
- To add fresh filter media
- To remove trapped dirt and debris that restrict flow (Correct answer)
- To increase chlorine output
- To reduce water temperature
Correct answer: To remove trapped dirt and debris that restrict flow
Backwashing reverses water flow through the filter to flush out accumulated debris, restoring flow rate and filtration efficiency.
Question 5: At what pH level does chlorine become LEAST effective as a disinfectant?
- 6.8
- 7.2
- 7.6
- 8.0 or above (Correct answer)
Correct answer: 8.0 or above
As pH rises above 7.8–8.0, hypochlorous acid (the active form of chlorine) converts to the much weaker hypochlorite ion, drastically reducing disinfection.
Question 6: How often should a pool operator visually inspect drain covers and sumps under normal operating conditions?
- Once per season
- Once per month
- Daily or at each pre-opening inspection (Correct answer)
- Weekly
Correct answer: Daily or at each pre-opening inspection
ANSI/APSP standards and the Virginia Graeme Baker Act require daily inspection of drain covers to ensure they are secure and undamaged.
Question 7: Which chemical is used to RAISE pH in a swimming pool?
- Muriatic acid
- Sodium bisulfate
- Sodium carbonate (soda ash) (Correct answer)
- Carbon dioxide
Correct answer: Sodium carbonate (soda ash)
Sodium carbonate (soda ash) is an alkaline compound that raises pool pH when added to the water.
NASCO Facility Operations & Maintenance 2
What is the recommended free chlorine residual range for a public swimming pool in most US states?