NASCO Water Chemistry & Quality Control 2

Question 1

What is the recommended combined chlorine (chloramine) level that should trigger superchlorination or breakpoint chlorination?

Accepted Answer

0.2 ppm

Answer

When combined chlorine reaches 0.2 ppm or higher, breakpoint chlorination should be performed to eliminate chloramines.

Question 2

The Langelier Saturation Index (LSI) is used to determine which water condition?

Accepted Answer

Water balance and corrosivity/scale potential

Answer

The LSI measures whether pool water is balanced, corrosive, or scale-forming based on pH, alkalinity, calcium hardness, and temperature.

Question 3

Which chemical is added to pool water to RAISE total alkalinity?

Accepted Answer

Sodium bicarbonate

Answer

Sodium bicarbonate (baking soda) is the standard chemical used to raise total alkalinity in pool water.

Question 4

At what water temperature does chlorine lose effectiveness most rapidly?

Accepted Answer

Above 84°F (29°C)

Answer

Chlorine dissipates much faster at higher temperatures (above 84°F), requiring more frequent testing and dosing.

Question 5

What does a DPD (N,N-diethyl-p-phenylenediamine) test kit measure?

Accepted Answer

Free and total chlorine levels

Answer

DPD reagents react with chlorine to produce a color change, allowing measurement of free and total chlorine concentrations.

(NASCO) National Aquatic Safety Company Aquatic Facility Operator Certification Practice Test