CPI Water Balance & Chemical Testing 3 — Questions and Answers
Question 1: The Langelier Saturation Index (LSI) value of +0.5 indicates pool water is:
- Perfectly balanced
- Slightly corrosive to pool surfaces
- Slightly scale-forming (Correct answer)
- Severely undersaturated
Correct answer: Slightly scale-forming
A positive LSI value indicates supersaturation with calcium carbonate, meaning the water has a tendency to deposit scale on pool surfaces and equipment.
Question 2: For a spa operating at 104°F, how do recommended free chlorine levels typically compare to a pool at 78°F?
- Lower, because heat activates chlorine
- The same; temperature has no effect on chlorine requirements
- Higher, because heat accelerates chlorine degradation and pathogen growth (Correct answer)
- Lower, because fewer bathers use spas
Correct answer: Higher, because heat accelerates chlorine degradation and pathogen growth
Higher water temperatures accelerate chlorine decomposition and increase microbial activity, so spas generally require more frequent chlorine monitoring and higher minimum residuals.
Question 3: Which of the following chlorine compounds also contributes to cyanuric acid levels in pool water?
- Calcium hypochlorite
- Sodium hypochlorite
- Trichloro-s-triazinetrione (trichlor) (Correct answer)
- Lithium hypochlorite
Correct answer: Trichloro-s-triazinetrione (trichlor)
Trichlor is a stabilized chlorine compound that contains cyanuric acid as part of its chemical structure, adding CYA to the water with each dose.
Question 4: A pool water sample shows combined chlorine of 0.8 ppm and free chlorine of 1.5 ppm. What does this indicate?
- The pool is properly breakpoint chlorinated
- Significant chloramine formation is present (Correct answer)
- The pool has zero sanitizing capacity
- Cyanuric acid levels are undetectable
Correct answer: Significant chloramine formation is present
Combined chlorine above 0.2 ppm indicates significant chloramine buildup, which causes eye irritation and the characteristic 'pool smell.'
Question 5: What minimum free chlorine concentration is generally required to achieve breakpoint chlorination and destroy chloramines?
- 3 times the combined chlorine level
- 5 times the combined chlorine level
- 10 times the combined chlorine level (Correct answer)
- Equal to the combined chlorine level
Correct answer: 10 times the combined chlorine level
Breakpoint chlorination requires adding enough chlorine to reach approximately 10 times the combined chlorine level to oxidize and destroy chloramines.
Question 6: An inspector tests a commercial pool and finds the cyanuric acid level at 200 ppm. The BEST recommendation is to:
- Add more stabilizer to maximize chlorine protection
- Partially drain and refill the pool to dilute CYA (Correct answer)
- Switch to a non-chlorine sanitizer immediately
- Increase the chlorine level to compensate
Correct answer: Partially drain and refill the pool to dilute CYA
Excessive cyanuric acid (above 100 ppm in most codes) cannot be chemically removed and requires dilution by partially draining and refilling with fresh water.
Question 7: Total dissolved solids (TDS) in pool water above 2,000 ppm above the source water level typically causes which issue?
- Skin rashes in swimmers
- Reduced effectiveness of pool chemicals and potential corrosion (Correct answer)
- Excessive algae growth
- False-high chlorine readings on test kits
Correct answer: Reduced effectiveness of pool chemicals and potential corrosion
Elevated TDS interferes with chemical balance, can reduce sanitizer effectiveness, and may lead to equipment corrosion and water that feels heavy or dull.
CPI Water Balance & Chemical Testing 3
The Langelier Saturation Index (LSI) value of +0.5 indicates pool water is: