CAT Aquatic Technicians Skills and Knowledge Areas 2 — Questions and Answers
Question 1: A pool's total alkalinity reads 60 ppm. What is the most likely consequence if left uncorrected?
- pH will become highly stable and resistant to change
- pH will fluctuate widely and be difficult to control (Correct answer)
- Chlorine demand will decrease significantly
- Calcium hardness will automatically increase
Correct answer: pH will fluctuate widely and be difficult to control
Low total alkalinity (below 80 ppm) causes pH to bounce dramatically, making water chemistry difficult to manage.
Question 2: Which type of filter media requires backwashing to clean and uses the finest filtration of the three common types?
- Sand
- Cartridge
- Diatomaceous Earth (DE) (Correct answer)
- Zeolite
Correct answer: Diatomaceous Earth (DE)
DE filters provide the finest filtration (3–5 microns) and are cleaned by backwashing, after which fresh DE must be added.
Question 3: When shocking a pool with calcium hypochlorite, a technician should always:
- Add the shock directly to the skimmer basket
- Pre-dissolve the shock in a bucket of pool water before adding (Correct answer)
- Add shock while the pump is off to allow it to settle
- Mix shock with muriatic acid first to boost effectiveness
Correct answer: Pre-dissolve the shock in a bucket of pool water before adding
Pre-dissolving calcium hypochlorite prevents bleaching of the pool surface and ensures even distribution.
Question 4: A residential pool pump is running but flow rate has dropped significantly. The filter pressure gauge reads normal. What is the most likely cause?
- Worn pump impeller or clogged pump strainer basket (Correct answer)
- Filter media needs replacement
- Heater bypass valve is open
- Cyanuric acid levels are too high
Correct answer: Worn pump impeller or clogged pump strainer basket
A clogged pump strainer basket or worn impeller restricts water intake, reducing flow rate while filter pressure may appear unaffected.
Question 5: What is the recommended free chlorine level (in ppm) for a residential swimming pool according to standard industry guidelines?
- 0.5–1.0 ppm
- 1.0–3.0 ppm (Correct answer)
- 3.5–5.0 ppm
- 5.0–8.0 ppm
Correct answer: 1.0–3.0 ppm
The standard recommended free chlorine range for residential pools is 1.0–3.0 ppm to ensure effective sanitation without irritation.
Question 6: Cyanuric acid (CYA) is used in outdoor pools primarily to:
- Increase total alkalinity without affecting pH
- Stabilize chlorine against UV degradation from sunlight (Correct answer)
- Prevent calcium scaling on pool surfaces
- Enhance the effectiveness of algaecides
Correct answer: Stabilize chlorine against UV degradation from sunlight
Cyanuric acid bonds with free chlorine, protecting it from UV degradation and extending its effectiveness in outdoor pools.
Question 7: A pool technician notices a strong chlorine odor and swimmer eye irritation despite a free chlorine reading of 3.0 ppm. What is the most likely cause?
- Free chlorine is too high
- High concentration of chloramines (combined chlorine) (Correct answer)
- pH is above 8.0
- Calcium hardness is too low
Correct answer: High concentration of chloramines (combined chlorine)
Chloramines (combined chlorine) cause the harsh odor and irritation associated with 'too much chlorine' — the fix is breakpoint chlorination, not reduction.
CAT Aquatic Technicians Skills and Knowledge Areas 2
A pool's total alkalinity reads 60 ppm.
What is the most likely consequence if left uncorrected?