Case Analysis & Practical Application Flashcards

A pool operator notices the water is cloudy and the filter pressure gauge reads 12 psi above the clean starting pressure. What is the FIRST corrective action?

Answer: Backwash or clean the filter

A filter pressure reading 8–10 psi above the clean baseline indicates the filter is dirty and should be backwashed or cleaned before other treatments.

During a routine inspection a CPO finds the pool pH is 8.4 and chlorine residual is 1.5 ppm. Swimmers report eye irritation. What is the most likely cause?

Answer: High pH is reducing the effectiveness of the available chlorine

At pH 8.4 only about 3% of chlorine exists as hypochlorous acid (the active sanitizer), making it far less effective and potentially causing irritation due to inadequate disinfection.

A hotel spa pool holds 2,000 gallons and the bather load is 10 people at a time. The required turnover rate is 30 minutes. What minimum flow rate must the circulation pump deliver?

Answer: 67 GPM

Flow rate = volume ÷ turnover time = 2,000 gal ÷ 30 min ≈ 67 GPM.

A CPO measures total alkalinity at 40 ppm. Which condition is MOST likely to result from this reading?

Answer: pH drift and difficulty maintaining stable pH

Low total alkalinity (below 80 ppm) acts as a poor buffer, causing rapid and unpredictable pH fluctuations that are hard to control.

After a fecal incident involving formed stool in a public pool, what is the recommended free chlorine level and contact time for remediation according to CDC guidelines?

Answer: 2 ppm for 25 minutes at pH 7.5

CDC recommends raising free chlorine to 2 ppm and maintaining it for 25 minutes at pH 7.5 or below to inactivate pathogens from a formed-stool fecal incident.

A pool's Langelier Saturation Index (LSI) is calculated at +0.8. What problem is MOST likely to develop?

Answer: Scale deposits on pool surfaces and equipment

An LSI above +0.3 indicates oversaturated water that is prone to forming calcium carbonate scale on surfaces and heat exchangers.

An outdoor pool has cyanuric acid (CYA) at 120 ppm. What action should the operator take?

Answer: Partially drain and refill the pool to dilute CYA

CYA above 100 ppm over-stabilizes chlorine, dramatically reducing its sanitizing ability; the only practical correction is dilution by partial drain and refill.