Water Chemistry & Quality Control Flashcards

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

Answer: 0.2 ppm

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

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

Answer: Water balance and corrosivity/scale potential

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

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

Answer: Sodium bicarbonate

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

At what water temperature does chlorine lose effectiveness most rapidly?

Answer: Above 84°F (29°C)

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

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

Answer: Free and total chlorine levels

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

Cyanuric acid (stabilizer) in outdoor pools should typically be maintained within what range?

Answer: 30–50 ppm

Cyanuric acid is recommended at 30–50 ppm for outdoor pools to protect chlorine from UV degradation without over-stabilizing.

When shocking a pool with calcium hypochlorite, why should it be pre-dissolved in a bucket of water before adding to the pool?

Answer: To prevent bleaching or damage to pool surfaces

Pre-dissolving calcium hypochlorite prevents concentrated product from settling on pool surfaces and causing bleaching or etching.