CPO Water Testing and Analysis 2 — Questions and Answers
Question 1: What is the recommended pH range for public swimming pool water according to standard CPO guidelines?
- 7.2–7.8 (Correct answer)
- 6.5–7.2
- 7.8–8.2
- 6.8–7.0
Correct answer: 7.2–7.8
The CDC and PHTA recommend maintaining pool pH between 7.2 and 7.8 for effective disinfection and swimmer comfort.
Question 2: What is the standard target range for total alkalinity in a public swimming pool?
- 40–60 ppm
- 60–80 ppm
- 80–120 ppm (Correct answer)
- 150–200 ppm
Correct answer: 80–120 ppm
Total alkalinity should be maintained between 80 and 120 ppm to stabilize pH and prevent rapid fluctuations.
Question 3: Which of the following does a DPD (N,N-diethyl-p-phenylenediamine) test kit measure?
- Combined chlorine only
- Total chlorine only
- Cyanuric acid levels only
- Both free chlorine and total chlorine (Correct answer)
Correct answer: Both free chlorine and total chlorine
DPD reagents measure free chlorine directly; adding a second reagent (potassium iodide) allows measurement of total chlorine to calculate combined chlorine.
Question 4: What is the recommended calcium hardness range for swimming pools to prevent corrosion and scale formation?
- 100–150 ppm
- 150–200 ppm
- 200–400 ppm (Correct answer)
- 400–600 ppm
Correct answer: 200–400 ppm
Calcium hardness between 200 and 400 ppm protects pool surfaces from corrosive low-calcium water and prevents scale deposits from high-calcium water.
Question 5: When using a DPD test kit, the presence of free chlorine causes the water sample to turn which color?
- Yellow
- Pink or red (Correct answer)
- Blue
- Colorless
Correct answer: Pink or red
DPD reagent reacts with free chlorine to produce a pink-to-red color; the deeper the color, the higher the chlorine concentration.
Question 6: The OTO (orthotolidine) reagent tests for which water parameter?
- Total chlorine (Correct answer)
- Free chlorine only
- pH level
- Combined chlorine only
Correct answer: Total chlorine
OTO reacts with all forms of chlorine (free and combined) and turns yellow, measuring total chlorine; it cannot differentiate free from combined chlorine.
Question 7: When collecting a pool water sample for chemical testing, where should the sample be taken?
- From the surface near the main skimmer
- At elbow depth (about 18 inches) away from return inlets and skimmers (Correct answer)
- From the deep end near the pool floor
- Directly from an active return jet
Correct answer: At elbow depth (about 18 inches) away from return inlets and skimmers
Sampling at elbow depth away from inlets and returns provides a representative mid-pool reading unaffected by concentrated chemical inputs.
CPO Water Testing and Analysis 2
What is the recommended pH range for public swimming pool water according to standard CPO guidelines?