NGWA Water Systems Certification
Exam (Less Than 100 GPM – Exam K) –
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a pressure tank in a water system?
A. Increase water flow
B. Maintain system pressure and reduce pump cycling
C. Filter impurities
D. Prevent backflow
Rationale: A pressure tank stores water under pressure to maintain
consistent system pressure and minimize pump on/off cycles.
2. What is the typical maximum flow rate for a system classified as “less
than 100 GPM”?
A. 50 GPM
, B. 150 GPM
C. 100 GPM
D. 99 GPM
Rationale: The system is defined as less than 100 GPM, so the
maximum is 99 GPM.
3. Which component prevents backflow from the water system into the
public supply?
A. Pump
B. Check valve
C. Backflow preventer
D. Pressure switch
Rationale: A backflow preventer protects the source water from
contamination by preventing reverse flow.
4. What is the main function of a check valve in a pump system?
A. Regulate pressure
B. Filter debris
C. Prevent reverse flow
D. Measure flow rate
Rationale: Check valves allow water to flow in one direction only,
preventing backflow that could damage the pump or system.
5. Which factor is most important when selecting a well pump for a small
water system?
A. Color of the pump
, B. Required flow rate and total dynamic head
C. Brand popularity
D. Pipe diameter only
Rationale: Pumps must meet the system’s required flow and
overcome the total dynamic head to operate efficiently.
6. What does TDH stand for in water system design?
A. Total Dynamic Height
B. Total Drainage Head
C. Total Dynamic Head
D. Total Depth Hydraulic
Rationale: Total Dynamic Head is the sum of the vertical lift, friction
losses, and pressure requirements of the system.
7. What is the typical purpose of a sediment filter in a water system?
A. Adjust pH
B. Remove suspended solids
C. Kill bacteria
D. Increase pressure
Rationale: Sediment filters remove dirt, sand, and other particles to
protect downstream equipment.
8. Which water quality parameter is commonly measured to determine
hardness?
A. pH
B. Calcium and magnesium concentration
, C. Nitrate concentration
D. Turbidity
Rationale: Hardness is caused primarily by calcium and magnesium
ions in water.
9. What is the primary function of a pressure switch in a residential
water system?
A. Turn the pump on/off based on system pressure
B. Filter water
C. Increase flow rate
D. Prevent backflow
Rationale: The pressure switch activates or deactivates the pump to
maintain the desired pressure range.
10. What is a common symptom of air in a water system?
A. Water discoloration
B. Spitting faucets or noisy pipes
C. Low pH
D. Slow pump start only
Rationale: Air trapped in pipes can cause noise, water hammer, and
irregular flow.
11. Which material is commonly used for potable water piping in
small systems?
A. Lead
B. Cast iron
Exam (Less Than 100 GPM – Exam K) –
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the primary purpose of a pressure tank in a water system?
A. Increase water flow
B. Maintain system pressure and reduce pump cycling
C. Filter impurities
D. Prevent backflow
Rationale: A pressure tank stores water under pressure to maintain
consistent system pressure and minimize pump on/off cycles.
2. What is the typical maximum flow rate for a system classified as “less
than 100 GPM”?
A. 50 GPM
, B. 150 GPM
C. 100 GPM
D. 99 GPM
Rationale: The system is defined as less than 100 GPM, so the
maximum is 99 GPM.
3. Which component prevents backflow from the water system into the
public supply?
A. Pump
B. Check valve
C. Backflow preventer
D. Pressure switch
Rationale: A backflow preventer protects the source water from
contamination by preventing reverse flow.
4. What is the main function of a check valve in a pump system?
A. Regulate pressure
B. Filter debris
C. Prevent reverse flow
D. Measure flow rate
Rationale: Check valves allow water to flow in one direction only,
preventing backflow that could damage the pump or system.
5. Which factor is most important when selecting a well pump for a small
water system?
A. Color of the pump
, B. Required flow rate and total dynamic head
C. Brand popularity
D. Pipe diameter only
Rationale: Pumps must meet the system’s required flow and
overcome the total dynamic head to operate efficiently.
6. What does TDH stand for in water system design?
A. Total Dynamic Height
B. Total Drainage Head
C. Total Dynamic Head
D. Total Depth Hydraulic
Rationale: Total Dynamic Head is the sum of the vertical lift, friction
losses, and pressure requirements of the system.
7. What is the typical purpose of a sediment filter in a water system?
A. Adjust pH
B. Remove suspended solids
C. Kill bacteria
D. Increase pressure
Rationale: Sediment filters remove dirt, sand, and other particles to
protect downstream equipment.
8. Which water quality parameter is commonly measured to determine
hardness?
A. pH
B. Calcium and magnesium concentration
, C. Nitrate concentration
D. Turbidity
Rationale: Hardness is caused primarily by calcium and magnesium
ions in water.
9. What is the primary function of a pressure switch in a residential
water system?
A. Turn the pump on/off based on system pressure
B. Filter water
C. Increase flow rate
D. Prevent backflow
Rationale: The pressure switch activates or deactivates the pump to
maintain the desired pressure range.
10. What is a common symptom of air in a water system?
A. Water discoloration
B. Spitting faucets or noisy pipes
C. Low pH
D. Slow pump start only
Rationale: Air trapped in pipes can cause noise, water hammer, and
irregular flow.
11. Which material is commonly used for potable water piping in
small systems?
A. Lead
B. Cast iron
