Licensing Exam Practice Questions And

Public Water System Operator Class C Licensing Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a water distribution system?

a) Remove all minerals from water

b) Deliver potable water to consumers

c) Treat wastewater

d) Monitor rainfall

Rationale: The primary function of a water distribution system is to deliver

safe, potable water to consumers while maintaining adequate pressure and flow.

• Which of the following is the most common method for disinfecting

drinking water? 1 / 4

a) Filtration

b) Chlorination

c) Sedimentation

d) Fluoridation

Rationale: Chlorination is widely used to disinfect water because it is

effective against bacteria and viruses and provides residual protection.

• The safe residual chlorine level in a water distribution system is

typically:

• 0.1–0.2 mg/L
• 0.3–0.5 mg/L
• 0.2–1.0 mg/L
• 1.5–2.5 mg/L

Rationale: Maintaining 0.2–1.0 mg/L of chlorine residual ensures

disinfection without producing excessive taste or odor issues.

• What is turbidity in water?

a) The acidity level

b) The cloudiness or suspended particles in water

c) The temperature

d) The dissolved oxygen content

Rationale: Turbidity measures the cloudiness caused by suspended

particles and can indicate potential microbial contamination. 2 / 4

• What is the most common source of microbial contamination in a

public water system?

a) Industrial discharge

b) Agricultural runoff

c) Fecal matter from humans or animals

d) Heavy metals

Rationale: Fecal contamination introduces bacteria, viruses, and protozoa

that can cause waterborne diseases.

• Which of the following is an approved method for measuring water

pH?

a) Conductivity meter

b) Turbidity meter

• pH meter or pH test strips

d) Chlorine test kit

Rationale: pH meters or properly calibrated pH test strips accurately

measure the hydrogen ion concentration in water.

• The process of removing large suspended solids from raw water

before treatment is called:

a) Filtration

b) Screening

c) Chlorination

d) Softening 3 / 4

Rationale: Screening removes large debris such as leaves, sticks, and trash

before the water enters treatment processes.

• Which of the following waterborne diseases is most commonly

associated with Giardia lamblia?

a) Cholera

b) Hepatitis A

c) Giardiasis

d) Typhoid

Rationale: Giardia lamblia is a protozoan parasite that causes

gastrointestinal illness called giardiasis.

• What is the main purpose of a backflow prevention device?

a) Increase water pressure

b) Prevent contamination of the potable water system

c) Measure flow rate

d) Filter sediment

Rationale: Backflow prevention devices protect potable water from

contamination due to reverse flow from cross-connections.

10. Water hardness is primarily caused by:

a) Sodium and potassium

b) Calcium and magnesium ions

c) Chlorine

d) Fluoride

• / 4