Contractor Exam Questions And

CA C42 Sanitation Systems Contractor Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

• Which of the following is the primary purpose of a septic tank?
• Store drinking water
• Separate solids from liquids in wastewater
• Filter stormwater
• Aerate wastewater

Rationale: A septic tank is designed to separate solids from liquids in

household wastewater before discharge into a drain field.

• What is the minimum slope recommended for a residential sewer

lateral?

• 1/16 inch per foot
• 1/32 inch per foot
• 1/4 inch per foot
• 1 inch per foot

Rationale: A slope of 1/4 inch per foot ensures proper gravity flow

and reduces the risk of clogging.

• Which material is commonly used for residential sewer pipes?
• Copper
• Aluminum

C) PVC

• Steel

Rationale: PVC (Polyvinyl Chloride) is widely used due to durability,

corrosion resistance, and ease of installation. 1 / 3

• What is the main function of a grease interceptor?
• Filter drinking water
• Store wastewater
• Trap fats, oils, and grease before entering the sewer system
• Treat stormwater runoff

Rationale: Grease interceptors prevent fats and oils from clogging

sewer systems.

• How often should a septic tank typically be pumped?
• Every year
• Every 2–3 years
• Every 3–5 years
• Every 10 years

Rationale: Pumping every 3–5 years removes accumulated solids and

prevents system failure.

• Which method is most effective for testing a sewer line for leaks?
• Visual inspection
• Air or water pressure testing
• Thermal imaging
• Sound detection

Rationale: Air or water pressure tests can accurately detect leaks in a

sewer line.

• What is the recommended minimum distance between a septic tank and

a drinking water well?

• 10 feet
• 25 feet
• 50 feet
• 100 feet

Rationale: A minimum of 50 feet reduces the risk of groundwater

contamination.

• What type of vent is required for a sanitation system to prevent

siphoning of traps?

• Floor vent
• Vent stack
• Roof drain
• Overflow vent

Rationale: Vent stacks allow air to enter the plumbing system and

prevent siphoning of water traps. 2 / 3

• Which is a common cause of sewer backup in residential systems?
• Excess rainfall
• Broken water meter
• Root intrusion
• Leaking roof

Rationale: Tree roots can penetrate joints, blocking sewer flow and

causing backups.

• What is the standard pipe diameter for a residential building

drain?

• 2 inches
• 3–4 inches
• 5 inches
• 6 inches

Rationale: Residential building drains typically use 3–4 inch pipes to

handle wastewater efficiently.

• Which chemical is safe for regular maintenance of septic

systems?

• Strong bleach
• Acid
• Bacterial additives
• Solvent-based cleaners

Rationale: Bacterial additives help maintain the natural digestion

process in septic tanks.

• What is the purpose of a cleanout in a sewer system?
• Vent gases
• Provide access for clearing blockages
• Measure flow rate
• Filter solids

Rationale: Cleanouts allow easy access for cleaning and maintenance

of sewer lines.

• Which soil type is most suitable for a leach field?
• Clay
• Sandy loam
• Rock
• Silt

Rationale: Sandy loam allows proper percolation while filtering

wastewater effectively.

• / 3