CPI Water Quality & Treatment Standards 2 — Questions and Answers
Question 1: What is the recommended cyanuric acid (stabilizer) concentration range for outdoor residential pools?
- 10–30 ppm
- 30–50 ppm (Correct answer)
- 60–80 ppm
- 100–120 ppm
Correct answer: 30–50 ppm
Cyanuric acid should be kept between 30–50 ppm to effectively stabilize chlorine without over-inhibiting its sanitizing ability.
Question 2: A pool inspector notices the water is cloudy but the chlorine reading is within range. Which parameter should be checked next?
- Salt level
- Filtration turnover rate and filter condition (Correct answer)
- Heater temperature
- Pump motor amperage
Correct answer: Filtration turnover rate and filter condition
Cloudy water with adequate chlorine typically indicates inadequate filtration, a dirty filter, or insufficient turnover rate.
Question 3: Which condition describes 'combined chlorine' (chloramines) in pool water?
- Free chlorine that has not yet reacted
- Chlorine bound to ammonia or nitrogen compounds (Correct answer)
- Hypochlorous acid at low pH
- Chlorine gas dissolved above the waterline
Correct answer: Chlorine bound to ammonia or nitrogen compounds
Combined chlorine forms when free chlorine reacts with ammonia or nitrogenous waste, producing chloramines that cause odor and eye irritation.
Question 4: What is the minimum free chlorine level recommended by the Model Aquatic Health Code (MAHC) for a public pool?
- 0.5 ppm
- 1.0 ppm (Correct answer)
- 3.0 ppm
- 5.0 ppm
Correct answer: 1.0 ppm
The MAHC recommends a minimum free chlorine level of 1.0 ppm for public pools to ensure adequate disinfection.
Question 5: An inspector finds a pool's total alkalinity at 220 ppm. What is the primary concern?
- pH will be extremely difficult to raise
- pH will resist adjustment and scale formation is likely (Correct answer)
- Chlorine will evaporate faster
- Algae growth is immediately expected
Correct answer: pH will resist adjustment and scale formation is likely
High total alkalinity (above 180 ppm) causes pH to resist change ('pH lock') and promotes calcium carbonate scale formation.
Question 6: Breakpoint chlorination requires adding chlorine to achieve what ratio relative to combined chlorine?
- 1:1 (equal parts)
- 5:1 (five times the combined chlorine)
- 7.6:1 (approximately 10 times) (Correct answer)
- 20:1
Correct answer: 7.6:1 (approximately 10 times)
Breakpoint chlorination requires adding approximately 7.6–10 times the combined chlorine level to oxidize and destroy chloramines.
Question 7: Which chemical is used to LOWER pool water pH?
- Sodium carbonate (soda ash)
- Sodium bicarbonate
- Muriatic acid (hydrochloric acid) (Correct answer)
- Calcium hypochlorite
Correct answer: Muriatic acid (hydrochloric acid)
Muriatic acid (hydrochloric acid) is the most common chemical used to lower pH in pool water.
CPI Water Quality & Treatment Standards 2
What is the recommended cyanuric acid (stabilizer) concentration range for outdoor residential pools?