Contractor Exam Questions And

CA D35 Pool And Spa Maintenance Contractor Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

What is the ideal pH range for a swimming pool?

A. 6.0–6.5

B. 6.8–7.0

C. 7.2–7.8

D. 8.0–8.5

C. 7.2–7.8

Rationale: Maintaining a pH between 7.2 and 7.8 ensures swimmer

comfort and optimal chlorine efficiency.

• Which chemical is commonly used to sanitize pools?
• Sodium bicarbonate
• Calcium chloride
• Chlorine
• Sodium hydroxide
• Chlorine

Rationale: Chlorine is the most widely used sanitizer for killing

bacteria and algae in pool water.

• What is the main purpose of a pool skimmer?
• Circulate water
• Remove debris from the surface
• Measure water chemistry
• Heat the pool 1 / 3

• Remove debris from the surface

Rationale: Skimmers trap leaves, insects, and other debris before they

sink to the bottom.

• How often should pool water be tested for pH and chlorine levels?
• Once a month
• Once a week
• Daily
• Every six months
• Daily

Rationale: Daily testing helps maintain safe chemical levels and

prevents water quality issues.

• Which type of filter uses sand to remove impurities?
• Cartridge filter
• Diatomaceous earth filter
• Sand filter
• Media filter
• Sand filter

Rationale: Sand filters trap particles as water passes through a bed of

sand.

• What is the main cause of cloudy pool water?
• High chlorine
• High calcium hardness
• Improper filtration or chemical imbalance
• Low water temperature
• Improper filtration or chemical imbalance

Rationale: Cloudiness usually occurs due to poor filtration or

incorrect chemical levels, leading to suspended particles.

• What does the term “superchlorination” or “shocking” mean?
• Reducing chlorine levels
• Adding a large dose of chlorine
• Lowering pH
• Increasing water temperature
• Adding a large dose of chlorine

Rationale: Shocking eliminates bacteria, algae, and chloramines by

temporarily raising chlorine levels.

• What is the recommended sanitizer level for a residential pool?
• 0.5–1 ppm 2 / 3

• 1–3 ppm
• 3–5 ppm
• 5–10 ppm
• 1–3 ppm

Rationale: 1–3 ppm free chlorine is sufficient for safe residential pool

water sanitation.

• Which device prevents backflow of pool water into the public water

supply?

• Check valve
• Flow meter
• Vacuum pump
• Skimmer
• Check valve

Rationale: A check valve ensures water only flows in one direction,

preventing contamination.

• What is the purpose of cyanuric acid in outdoor pools?
• Raise pH
• Stabilize chlorine against sunlight degradation
• Lower alkalinity
• Prevent algae growth directly
• Stabilize chlorine against sunlight degradation

Rationale: Cyanuric acid protects chlorine from being broken down

by UV rays, extending its effectiveness.

10. Alkalinity in pool water primarily helps to:

• Raise calcium hardness
• Stabilize pH
• Reduce chlorine efficiency
• Remove algae
• Stabilize pH

Rationale: Total alkalinity buffers the water, preventing rapid pH

fluctuations.

• Which of the following is a common sign of algae growth?
• Clear water
• Green or black discoloration
• High chlorine
• Low pH
• Green or black discoloration
• / 3