COMMERCIAL PLUMBING QUALIFICATION EXAM LATEST
2026 VERSION WITH 100 QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED ANSWERS) |ALREADY
GRADED A+||BRAND NEW VERSION!!
1. Which type of pipe is most commonly used for commercial water supply
lines?
A. PVC
B. CPVC
C. Copper
D. Galvanized steel
C. Copper Copper is widely used in commercial water supply for its
durability, corrosion resistance, and suitability for both hot and cold water
systems.
2. What is the standard slope for horizontal drainage piping?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
C. 1/4 inch per foot A slope of 1/4 inch per foot ensures proper gravity flow
in horizontal drainage pipes, preventing clogs and backups.
3. What is the main purpose of a backflow preventer in a commercial
plumbing system?
A. Reduce water pressure
B. Prevent sewer gases
C. Prevent contaminated water from entering the potable water supply
D. Increase water flow
C. Prevent contaminated water from entering the potable water supply
, Backflow preventers protect drinking water from contamination due to
reverse flow or siphonage.
4. Which type of valve is commonly used to isolate a section of piping in
commercial systems?
A. Globe valve
B. Gate valve
C. Check valve
D. Pressure reducing valve
B. Gate valve Gate valves are ideal for on/off control in piping systems,
allowing isolation without pressure loss.
5. What is the minimum required size for a commercial water service line in
most buildings?
A. 3/4 inch
B. 1 inch
C. 1 1/2 inch
D. 2 inches
B. 1 inch Most commercial buildings require at least a 1-inch service line to
meet water demand, though larger systems may need bigger sizes.
6. Which of the following is a common material for commercial drain, waste,
and vent piping?
A. PVC
B. Cast iron
C. Copper
D. PEX
B. Cast iron Cast iron is durable, fire-resistant, and reduces noise, making it
ideal for commercial DWV systems.
7. What type of fixture requires an air gap to prevent backflow?
A. Toilet
B. Sinks with faucets
C. Floor drains
D. Water heaters
, B. Sinks with faucets An air gap ensures that contaminated water cannot
siphon back into the potable water supply.
8. Which fitting is used to change the direction of a drainage pipe by 90
degrees?
A. Wye
B. Tee
C. Elbow
D. Coupling
C. Elbow Elbows allow the pipe to change direction, commonly in 90- or 45-
degree angles.
9. What is the purpose of a grease interceptor in commercial kitchens?
A. Remove solids from water
B. Prevent grease from entering the sewer system
C. Increase water flow
D. Reduce water temperature
B. Prevent grease from entering the sewer system Grease interceptors trap
fats, oils, and grease, protecting plumbing and municipal sewer lines.
10.Which fixture requires a trap primer to maintain the water seal?
A. Floor drain
B. Toilet
C. Faucet
D. Shower
A. Floor drain Trap primers add water to traps in floor drains to prevent
sewer gases from escaping when infrequently used.
11.What is the primary function of a pressure reducing valve in commercial
plumbing?
A. Increase flow rate
B. Reduce water pressure to safe levels
C. Prevent backflow
D. Mix hot and cold water
2026 VERSION WITH 100 QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED ANSWERS) |ALREADY
GRADED A+||BRAND NEW VERSION!!
1. Which type of pipe is most commonly used for commercial water supply
lines?
A. PVC
B. CPVC
C. Copper
D. Galvanized steel
C. Copper Copper is widely used in commercial water supply for its
durability, corrosion resistance, and suitability for both hot and cold water
systems.
2. What is the standard slope for horizontal drainage piping?
A. 1/16 inch per foot
B. 1/8 inch per foot
C. 1/4 inch per foot
D. 1/2 inch per foot
C. 1/4 inch per foot A slope of 1/4 inch per foot ensures proper gravity flow
in horizontal drainage pipes, preventing clogs and backups.
3. What is the main purpose of a backflow preventer in a commercial
plumbing system?
A. Reduce water pressure
B. Prevent sewer gases
C. Prevent contaminated water from entering the potable water supply
D. Increase water flow
C. Prevent contaminated water from entering the potable water supply
, Backflow preventers protect drinking water from contamination due to
reverse flow or siphonage.
4. Which type of valve is commonly used to isolate a section of piping in
commercial systems?
A. Globe valve
B. Gate valve
C. Check valve
D. Pressure reducing valve
B. Gate valve Gate valves are ideal for on/off control in piping systems,
allowing isolation without pressure loss.
5. What is the minimum required size for a commercial water service line in
most buildings?
A. 3/4 inch
B. 1 inch
C. 1 1/2 inch
D. 2 inches
B. 1 inch Most commercial buildings require at least a 1-inch service line to
meet water demand, though larger systems may need bigger sizes.
6. Which of the following is a common material for commercial drain, waste,
and vent piping?
A. PVC
B. Cast iron
C. Copper
D. PEX
B. Cast iron Cast iron is durable, fire-resistant, and reduces noise, making it
ideal for commercial DWV systems.
7. What type of fixture requires an air gap to prevent backflow?
A. Toilet
B. Sinks with faucets
C. Floor drains
D. Water heaters
, B. Sinks with faucets An air gap ensures that contaminated water cannot
siphon back into the potable water supply.
8. Which fitting is used to change the direction of a drainage pipe by 90
degrees?
A. Wye
B. Tee
C. Elbow
D. Coupling
C. Elbow Elbows allow the pipe to change direction, commonly in 90- or 45-
degree angles.
9. What is the purpose of a grease interceptor in commercial kitchens?
A. Remove solids from water
B. Prevent grease from entering the sewer system
C. Increase water flow
D. Reduce water temperature
B. Prevent grease from entering the sewer system Grease interceptors trap
fats, oils, and grease, protecting plumbing and municipal sewer lines.
10.Which fixture requires a trap primer to maintain the water seal?
A. Floor drain
B. Toilet
C. Faucet
D. Shower
A. Floor drain Trap primers add water to traps in floor drains to prevent
sewer gases from escaping when infrequently used.
11.What is the primary function of a pressure reducing valve in commercial
plumbing?
A. Increase flow rate
B. Reduce water pressure to safe levels
C. Prevent backflow
D. Mix hot and cold water
