Kentucky Master Plumber Examination
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Filter sediment
C. Prevent sewer gases from entering the building
D. Improve drainage speed
Answer: C. Prevent sewer gases from entering the building
Rationale: A plumbing trap maintains a water seal that blocks harmful
and unpleasant sewer gases from traveling back through the drainage
system into occupied spaces. Every plumbing fixture connected to a
drainage system generally requires a properly installed trap unless
specifically exempted by code.
,2. Which fitting is commonly used to change the direction of water
flow by 90 degrees?
A. Coupling
B. Tee
C. Union
D. Elbow
Answer: D. Elbow
Rationale: An elbow fitting changes the direction of piping, most
commonly by 45 or 90 degrees. It is one of the most frequently used
fittings in both water distribution and drainage systems.
3. What is the minimum slope generally required for a 3-inch
horizontal drainage pipe?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
,Answer: B. 1/8 inch per foot
Rationale: Most plumbing codes require horizontal drainage piping 3
inches and larger to be installed with a minimum slope of 1/8 inch per
foot unless otherwise specified. This provides adequate flow while
minimizing solids accumulation.
4. Which valve is designed to prevent backflow caused by
backpressure or backsiphonage?
A. Gate valve
B. Globe valve
C. Ball valve
D. Backflow preventer
Answer: D. Backflow preventer
Rationale: A backflow preventer protects potable water supplies from
contamination by preventing water from reversing direction due to
pressure changes.
5. Which material is commonly approved for residential water service
piping?
, A. Black steel
B. Copper tubing
C. Cast iron
D. Clay pipe
Answer: B. Copper tubing
Rationale: Copper tubing has long been an accepted material for
potable water distribution because it is corrosion-resistant, durable, and
capable of maintaining water quality.
6. What is the purpose of a plumbing vent?
A. Increase water pressure
B. Filter wastewater
C. Maintain atmospheric pressure in the drainage system
D. Store wastewater
Answer: C. Maintain atmospheric pressure in the drainage system
Rationale: Vent piping allows air into the drainage system, preventing
trap siphonage, promoting proper drainage, and protecting trap seals.
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
1. What is the primary purpose of a plumbing trap?
A. Increase water pressure
B. Filter sediment
C. Prevent sewer gases from entering the building
D. Improve drainage speed
Answer: C. Prevent sewer gases from entering the building
Rationale: A plumbing trap maintains a water seal that blocks harmful
and unpleasant sewer gases from traveling back through the drainage
system into occupied spaces. Every plumbing fixture connected to a
drainage system generally requires a properly installed trap unless
specifically exempted by code.
,2. Which fitting is commonly used to change the direction of water
flow by 90 degrees?
A. Coupling
B. Tee
C. Union
D. Elbow
Answer: D. Elbow
Rationale: An elbow fitting changes the direction of piping, most
commonly by 45 or 90 degrees. It is one of the most frequently used
fittings in both water distribution and drainage systems.
3. What is the minimum slope generally required for a 3-inch
horizontal drainage pipe?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
,Answer: B. 1/8 inch per foot
Rationale: Most plumbing codes require horizontal drainage piping 3
inches and larger to be installed with a minimum slope of 1/8 inch per
foot unless otherwise specified. This provides adequate flow while
minimizing solids accumulation.
4. Which valve is designed to prevent backflow caused by
backpressure or backsiphonage?
A. Gate valve
B. Globe valve
C. Ball valve
D. Backflow preventer
Answer: D. Backflow preventer
Rationale: A backflow preventer protects potable water supplies from
contamination by preventing water from reversing direction due to
pressure changes.
5. Which material is commonly approved for residential water service
piping?
, A. Black steel
B. Copper tubing
C. Cast iron
D. Clay pipe
Answer: B. Copper tubing
Rationale: Copper tubing has long been an accepted material for
potable water distribution because it is corrosion-resistant, durable, and
capable of maintaining water quality.
6. What is the purpose of a plumbing vent?
A. Increase water pressure
B. Filter wastewater
C. Maintain atmospheric pressure in the drainage system
D. Store wastewater
Answer: C. Maintain atmospheric pressure in the drainage system
Rationale: Vent piping allows air into the drainage system, preventing
trap siphonage, promoting proper drainage, and protecting trap seals.
