CPI Water Balance & Chemical Testing 3

Question 1

The Langelier Saturation Index (LSI) value of +0.5 indicates pool water is:

Accepted Answer

Slightly scale-forming

Answer

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?

Accepted Answer

Higher, because heat accelerates chlorine degradation and pathogen growth

Answer

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?

Accepted Answer

Trichloro-s-triazinetrione (trichlor)

Answer

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?

Accepted Answer

Significant chloramine formation is present

Answer

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?

Accepted Answer

10 times the combined chlorine level

Answer

Breakpoint chlorination requires adding enough chlorine to reach approximately 10 times the combined chlorine level to oxidize and destroy chloramines.

(CPI) Certified Pool & Spa Inspector Practice Test

(CPI) Certified Pool & Spa Inspector Practice Test

CPI Water Balance & Chemical Testing 3