AL WS Water Systems Installer Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
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1. What is the primary purpose of a water distribution system?
a. To collect wastewater
b. To remove stormwater
c. To transport potable water to points of use
d. To treat sewage
Answer: c. To transport potable water to points of use
Rationale: A water distribution system is designed to convey treated,
potable water from its source or storage facility to buildings, fixtures,
and other approved points of use while maintaining adequate
pressure, flow, and water quality.
2. Which material is commonly used for underground potable-water
service piping?
,a. Ordinary garden hose
b. Approved PVC or other listed water-service piping
c. Unprotected electrical conduit
d. Untreated wood
Answer: b. Approved PVC or other listed water-service piping
Rationale: Underground water services must use piping approved for
potable-water service and suitable for the pressure, soil conditions,
and installation method. PVC is commonly used when it is properly
rated and approved for the application.
3. What is the main purpose of a shutoff valve on a water service?
a. Increase water temperature
b. Stop or control water flow
c. Remove dissolved minerals
d. Measure chlorine concentration
Answer: b. Stop or control water flow
Rationale: A shutoff valve allows the water supply to be isolated for
maintenance, repairs, emergencies, or replacement of downstream
components without necessarily shutting down the entire system.
4. Why should potable-water piping be protected from
contamination?
,a. To improve electrical conductivity
b. To prevent unsafe substances from entering the drinking-water
supply
c. To increase pipe weight
d. To reduce water temperature
Answer: b. To prevent unsafe substances from entering the drinking-
water supply
Rationale: Potable water must be protected from substances that
could adversely affect health. Cross-connections, backflow, improper
materials, and unsanitary installation practices can introduce
contaminants into the drinking-water system.
5. What is a cross-connection?
a. A connection between two approved water meters
b. A connection between a potable-water system and a potential
source of contamination
c. A connection between two identical valves
d. A connection between two electrical circuits
Answer: b. A connection between a potable-water system and a
potential source of contamination
, Rationale: A cross-connection creates a pathway through which
contaminated or nonpotable water could enter a potable-water
system. Proper separation and backflow protection are used to
eliminate or control this hazard.
6. What condition can cause backflow through a cross-connection?
a. Excessive pipe insulation
b. Backpressure or backsiphonage
c. Proper water pressure
d. Normal valve operation
Answer: b. Backpressure or backsiphonage
Rationale: Backflow can occur when pressure in the nonpotable
system becomes greater than potable-system pressure (backpressure),
or when negative pressure develops in the potable system and siphons
contaminants backward (backsiphonage).
7. What is the purpose of a backflow-prevention device?
a. To increase pipe diameter
b. To prevent reverse flow that could contaminate potable water
c. To heat the water supply
d. To remove sediment from wastewater
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
1. What is the primary purpose of a water distribution system?
a. To collect wastewater
b. To remove stormwater
c. To transport potable water to points of use
d. To treat sewage
Answer: c. To transport potable water to points of use
Rationale: A water distribution system is designed to convey treated,
potable water from its source or storage facility to buildings, fixtures,
and other approved points of use while maintaining adequate
pressure, flow, and water quality.
2. Which material is commonly used for underground potable-water
service piping?
,a. Ordinary garden hose
b. Approved PVC or other listed water-service piping
c. Unprotected electrical conduit
d. Untreated wood
Answer: b. Approved PVC or other listed water-service piping
Rationale: Underground water services must use piping approved for
potable-water service and suitable for the pressure, soil conditions,
and installation method. PVC is commonly used when it is properly
rated and approved for the application.
3. What is the main purpose of a shutoff valve on a water service?
a. Increase water temperature
b. Stop or control water flow
c. Remove dissolved minerals
d. Measure chlorine concentration
Answer: b. Stop or control water flow
Rationale: A shutoff valve allows the water supply to be isolated for
maintenance, repairs, emergencies, or replacement of downstream
components without necessarily shutting down the entire system.
4. Why should potable-water piping be protected from
contamination?
,a. To improve electrical conductivity
b. To prevent unsafe substances from entering the drinking-water
supply
c. To increase pipe weight
d. To reduce water temperature
Answer: b. To prevent unsafe substances from entering the drinking-
water supply
Rationale: Potable water must be protected from substances that
could adversely affect health. Cross-connections, backflow, improper
materials, and unsanitary installation practices can introduce
contaminants into the drinking-water system.
5. What is a cross-connection?
a. A connection between two approved water meters
b. A connection between a potable-water system and a potential
source of contamination
c. A connection between two identical valves
d. A connection between two electrical circuits
Answer: b. A connection between a potable-water system and a
potential source of contamination
, Rationale: A cross-connection creates a pathway through which
contaminated or nonpotable water could enter a potable-water
system. Proper separation and backflow protection are used to
eliminate or control this hazard.
6. What condition can cause backflow through a cross-connection?
a. Excessive pipe insulation
b. Backpressure or backsiphonage
c. Proper water pressure
d. Normal valve operation
Answer: b. Backpressure or backsiphonage
Rationale: Backflow can occur when pressure in the nonpotable
system becomes greater than potable-system pressure (backpressure),
or when negative pressure develops in the potable system and siphons
contaminants backward (backsiphonage).
7. What is the purpose of a backflow-prevention device?
a. To increase pipe diameter
b. To prevent reverse flow that could contaminate potable water
c. To heat the water supply
d. To remove sediment from wastewater
