Water Balance & Chemical Testing Flashcards

What is the recommended pH range for pool water according to most health codes and APSP standards?

Answer: 7.2–7.8

A pH of 7.2–7.8 is the standard recommended range, balancing sanitizer effectiveness and bather comfort.

When testing total alkalinity, a result of 40 ppm would most likely cause which problem?

Answer: Rapid, uncontrolled pH fluctuations

Low alkalinity (below 80 ppm) removes pH buffering capacity, causing pH to swing dramatically with minor chemical additions.

A DPD test kit measures which pool chemical parameter?

Answer: Free available chlorine

DPD (N,N-diethyl-p-phenylenediamine) reagent reacts with free available chlorine to produce a pink color for colorimetric testing.

Which reagent is used in the FAS-DPD test method to determine the exact chlorine concentration by titration?

Answer: Ferrous ammonium sulfate

FAS (ferrous ammonium sulfate) is the titrant that decolorizes the DPD-chlorine complex, allowing precise chlorine measurement.

A pool inspector observes milky white water in a freshly filled pool with a calcium hardness reading of 650 ppm. The MOST likely cause is:

Answer: Calcium carbonate precipitation

Extremely high calcium hardness combined with adequate alkalinity and pH can cause calcium carbonate to precipitate out of solution, creating cloudy water.

What effect does high cyanuric acid (stabilizer) have on chlorine's ability to kill pathogens?

Answer: It reduces the concentration of active hypochlorous acid

Cyanuric acid binds free chlorine, reducing the proportion of active hypochlorous acid (HOCl) and slowing disinfection rates.

When using test strips to check pool chemistry, the inspector should dip the strip and read results after how long?

Answer: After 15–30 seconds as directed by manufacturer

Test strip manufacturers typically specify a 15–30 second reaction time before comparing the color pads to the reference chart.