CPO Operation and Maintenance 3 — Questions and Answers
Question 1: An erosion (tablet) chemical feeder introduces disinfectant into pool water by which mechanism?
- Injecting liquid chlorine directly into the return line under pressure
- Passing water over or through solid chemical tablets that dissolve gradually (Correct answer)
- Spraying granular chlorine onto the pool surface via a misting nozzle
- Electrolyzing a salt-and-water solution to produce chlorine gas
Correct answer: Passing water over or through solid chemical tablets that dissolve gradually
An erosion feeder dissolves solid tablets (such as trichlor) by routing a bypass stream of water through a canister containing the tablets.
Question 2: A pool test shows total alkalinity at 220 ppm. Which chemical should be added to bring it into the recommended 80–120 ppm range?
- Soda ash (sodium carbonate)
- Sodium bicarbonate (baking soda)
- Muriatic acid (hydrochloric acid) or sodium bisulfate (Correct answer)
- Sodium hypochlorite (liquid chlorine)
Correct answer: Muriatic acid (hydrochloric acid) or sodium bisulfate
Muriatic acid or dry acid (sodium bisulfate) lowers total alkalinity; adding it in small doses with the pump running prevents localized pH crashes.
Question 3: Which maintenance task is required on a DAILY basis at a public swimming pool under most health codes?
- Chemically clean and inspect all filter cartridges
- Test and record water chemistry including pH and disinfectant levels (Correct answer)
- Replace all pool light fixtures and inspect underwater fittings
- Disassemble and lubricate the main circulation pump
Correct answer: Test and record water chemistry including pH and disinfectant levels
Health codes universally require water chemistry testing and log entries at least once daily (and often more frequently during operating hours) for public pools.
Question 4: What is the Langelier Saturation Index (LSI) used to determine about pool water?
- The concentration of free chlorine available as a sanitizer
- Whether water is scale-forming, corrosive, or balanced based on multiple chemical factors (Correct answer)
- The turbidity level and clarity of pool water
- The ratio of combined chlorine to total chlorine
Correct answer: Whether water is scale-forming, corrosive, or balanced based on multiple chemical factors
The LSI combines pH, calcium hardness, total alkalinity, temperature, and TDS to predict whether water will deposit calcium scale or corrode pool surfaces.
Question 5: A combined chlorine reading comes back at 0.6 ppm. What does this indicate and what action is required?
- Free chlorine is too high and the pool should be partially drained
- Chloramines have formed; shock treatment (breakpoint chlorination) is needed (Correct answer)
- pH is elevated and should be corrected with acid
- The filter needs backwashing to remove the chloramine residue
Correct answer: Chloramines have formed; shock treatment (breakpoint chlorination) is needed
Combined chlorine above 0.4 ppm signals chloramine buildup, which causes eye/skin irritation and reduces sanitizing effectiveness — shocking destroys the chloramines.
Question 6: When should a cartridge filter element be replaced rather than simply cleaned?
- After every 90 days of service regardless of condition
- When cleaning no longer restores adequate flow, or when pleats are torn or deformed (Correct answer)
- Every time the filter pressure rises above the starting pressure
- Only when the filter housing itself is replaced
Correct answer: When cleaning no longer restores adequate flow, or when pleats are torn or deformed
Cartridge elements should be replaced when acid or detergent cleaning can no longer restore normal flow rates, or when physical damage is visible on the pleats.
Question 7: Why is it important to brush pool walls and floor regularly as part of a maintenance routine?
- Brushing raises water temperature by increasing surface agitation
- Brushing dislodges biofilm and early-stage algae before they can anchor and spread (Correct answer)
- Brushing distributes pool chemicals that have settled on the bottom
- Brushing is primarily done to improve swimmer visibility and aesthetics
Correct answer: Brushing dislodges biofilm and early-stage algae before they can anchor and spread
Regular brushing prevents algae and biofilm from establishing on surfaces, reducing chemical demand and keeping the pool visually clear.
CPO Operation and Maintenance 3
An erosion (tablet) chemical feeder introduces disinfectant into pool water by which mechanism?