CPO Advanced Professional Practice 3 — Questions and Answers
Question 1: A pool operator wants to calculate the Langelier Saturation Index (LSI). Which set of factors is required?
- pH, temperature, calcium hardness, total alkalinity, TDS (Correct answer)
- Chlorine, pH, cyanuric acid, flow rate
- Temperature, chlorine demand, ORP, TDS
- Alkalinity, chlorine, stabilizer, bather load
Correct answer: pH, temperature, calcium hardness, total alkalinity, TDS
The LSI is calculated using pH, water temperature, calcium hardness, total alkalinity, and TDS to assess water balance and corrosion/scale potential.
Question 2: A pool using a saltwater chlorine generator (SWG) shows consistently low free chlorine despite the generator running at 100%. The MOST likely cause is:
- Excessively high cyanuric acid inhibiting chlorine activity
- Low salt concentration in the water (Correct answer)
- High calcium hardness blocking the cell
- pH that is too low reducing generation efficiency
Correct answer: Low salt concentration in the water
If CYA is very high, chlorine activity is suppressed, but low salt concentration directly reduces the amount of chlorine the electrolytic cell can generate.
Question 3: Under OSHA standards, which personal protective equipment (PPE) is required when handling concentrated (35%) sodium hypochlorite?
- Chemical-resistant gloves, goggles, and apron (Correct answer)
- Latex gloves and safety glasses only
- N95 respirator and hard hat
- UV-protective eyewear and waterproof boots
Correct answer: Chemical-resistant gloves, goggles, and apron
Concentrated hypochlorite is a strong oxidizer and corrosive; OSHA requires chemical-resistant gloves, splash goggles, and a protective apron to prevent skin and eye injury.
Question 4: A public pool must post maximum bather load (MBL) calculations. Using the standing room formula, a pool with 1,200 sq ft of surface area yields an MBL of:
- 200 bathers (Correct answer)
- 100 bathers
- 400 bathers
- 150 bathers
Correct answer: 200 bathers
The standing room formula uses 6 sq ft per bather: 1,200 ÷ 6 = 200 bathers maximum.
Question 5: A pool operator discovers that the ORP (oxidation-reduction potential) reading is 650 mV but free chlorine measures 1.5 ppm. The BEST explanation is:
- High CYA is reducing chlorine's oxidizing power despite adequate free chlorine (Correct answer)
- The ORP probe is calibrated incorrectly and should read higher
- Total dissolved solids are interfering with the free chlorine test
- The pool is in breakpoint chlorination and ORP will rise shortly
Correct answer: High CYA is reducing chlorine's oxidizing power despite adequate free chlorine
CYA binds free chlorine and lowers ORP; even with measurable free chlorine, high CYA reduces the electrochemical activity that ORP sensors detect.
Question 6: Which disinfection byproduct (DBP) is associated with the reaction of chlorine with nitrogen-containing compounds from bathers?
- Chloramines (combined chlorine) (Correct answer)
- Trihalomethanes only
- Chlorinated paraffins
- Bromate ions
Correct answer: Chloramines (combined chlorine)
Chloramines form when free chlorine reacts with nitrogen compounds (urea, sweat, urine) introduced by bathers, producing eye irritation and the characteristic pool odor.
Question 7: A pool operator is responding to a fecal incident involving formed stool. According to CDC Healthy Swimming guidelines, the pool should be:
- Closed and shock-treated to 2 ppm free chlorine at pH 7.5 for 25 minutes (Correct answer)
- Closed and shock-treated to 20 ppm free chlorine for 8 hours
- Skimmed, then reopened after 30 minutes
- Treated with algaecide and reopened immediately
Correct answer: Closed and shock-treated to 2 ppm free chlorine at pH 7.5 for 25 minutes
For formed-stool fecal incidents (non-diarrheal), CDC recommends raising free chlorine to 2 ppm at pH 7.5 for a 25-minute contact time before reopening.
CPO Advanced Professional Practice 3
A pool operator wants to calculate the Langelier Saturation Index (LSI).
Which set of factors is required?