ESTUDYR
ASPE CPD STUDY QUESTIONS AH MOST TESTED QUESTIONS
AND ANSWERS GRADED A+ WITH RATIONALES
Plumbing, Medical-Gas & Fire Protection — Intensive MCQ Bank
1
What is the specific weight of water (commonly used in building calculations)?
A. 8.34 lb/gal
B. 1000 kg/m³
C. 62.4 lb/ft³ ✅
D. 9.81 N/kg
Rationale: The specific weight (weight per unit volume) of water is 62.4 pounds per cubic foot.
2
After a water test of a storm and sanitary system, what test is recommended to prove the system is gas
tight?
A. Hydrostatic test at 100 psi
B. Smoke pressure test at 1 in WC ✅
C. Vacuum test at -5 psi
D. Dye test with fluorescein
Rationale: A smoke pressure test (≈1 in. water column) is commonly used to detect gas/air leaks after
water testing.
3
Is an air test acceptable for storm and sanitary systems if a water test is not possible?
A. No — never acceptable
B. Yes — at 5 psi if water test is not possible ✅
C. Yes — at 1 psi only
D. Only for vertical stacks, never for horizontal lines
Rationale: Air testing at 5 psi is an accepted alternative when water testing cannot be performed.
4
,ESTUDYR
What is the usual water test procedure for storm and sanitary piping (before concealment)?
A. 1 ft WC for 1 hour
B. Minimum 10 ft WC (except topmost 10 ft), not to exceed 100 ft WC; plugs for >100 ft. ✅
C. 200 ft WC for entire system
D. Only peppermint oil test is required
Rationale: Standard procedure is 10 ft WC minimum (with limits and plug requirements as described).
5
Why is a peppermint oil test sometimes used on piping?
A. It measures structural strength
B. It sterilizes the pipe
C. To detect leaks by smell after boiling peppermint oil in water ✅
D. As a pressure gauge replacement
Rationale: Peppermint oil vapor can indicate leak locations by smell, though it’s hard to pinpoint leaks.
6
What is the maximum recommended dead-end length from a vent connection to any future drain outlet
to prevent slime/sludge growth?
A. 6 inches
B. 2 feet ✅
C. 10 feet
D. 8 feet
Rationale: A 2-ft maximum dead-end avoids stagnation and biological growth, except when extended to
an accessible cleanout.
7
Which fitting must not be used in a vertical drain run because of flow crossover and pressure issues?
A. Sanitary tee
B. Double sanitary tee ✅
C. Long-radius wye
D. Combination wye and 1/8 bend (tee-wye)
Rationale: Double sanitary tees can cause crossover flows and unstable pressure when one branch
discharges and another does not.
,ESTUDYR
8
What slope corresponds to ~2 fps velocity for 3-inch and smaller pipes?
A. 1/8 in/ft
B. 1/4 in/ft ✅
C. 1/2 in/ft
D. 1/16 in/ft
Rationale: For smaller pipes (≤3 in), 1/4 in/ft slope is used to maintain ~2 fps scouring velocity.
9
For larger pipes, what slope corresponds to ~2 fps?
A. 1/2 in/ft
B. 1/8 in/ft ✅
C. 1/4 in/ft
D. 1/16 in/ft
Rationale: Larger pipes require less slope; 1/8 in/ft is typical for 4–6 in.
10
Where should cleanouts be provided? (Select the best summary)
A. Only at the base of stacks
B. Only outside buildings
C. At exit point, every change >45°, every 50 ft (≤4"), every 100 ft (>4"), base of stacks, at direction
changes; manholes for >10" underground. ✅
D. Only on horizontal runs
Rationale: Multiple cleanouts are required for access: exits, directional changes, set intervals, stack
bases, and manholes for large underground mains.
11
What size of cleanout is required for piping up to 4 inches?
A. 2 inch cleanout
B. Same size as the pipe (i.e., full size) ✅
C. 6 inch cleanout
D. 1 inch cleanout
Rationale: For pipes ≤4", cleanout is usually the same diameter; for larger pipes, a 4" cleanout is
typically adequate.
, ESTUDYR
12
If there is danger of sewage backflow into a building, what should be installed?
A. A check valve only
B. A backwater valve (BWV) or BWV + manually operated gate valve ✅
C. A relief vent only
D. A sanitary tee
Rationale: BWV prevents backflow without interfering with airflow; a gate valve adds positive manual
protection where history of backflow exists.
13
Branch connections to the house drain should be made at the upper portion of the pipe (above half to
two-thirds full) because:
A. Easier to install fittings
B. Lower water temperature
C. Less stoppage risk, less flow interference, and more area available to relieve pneumatic pressure
fluctuations ✅
D. It reduces corrosion
Rationale: Upper-level taps reduce stoppage likelihood and prevent flow interference and pressure
issues.
14
How many fixture units (FUs) are equivalent to 1 gpm of continuous or semicontinuous flow?
A. 1 FU
B. 2 FUs ✅
C. 5 FUs
D. 0.5 FU
Rationale: 2 FUs corresponds to 1 gpm continuous (used for pumps, ejectors, HVAC condensate etc).
15
Minimum slopes for building drains to maintain scouring velocity: which is correct?
A. All pipes 1/16 in/ft
B. 3" and smaller 1/8 in/ft, larger 1/16 in/ft
C. 3" & smaller 1/4 in/ft; 4–6" 1/8 in/ft; ≥8" 1/16 in/ft (2 fps scouring) ✅
ASPE CPD STUDY QUESTIONS AH MOST TESTED QUESTIONS
AND ANSWERS GRADED A+ WITH RATIONALES
Plumbing, Medical-Gas & Fire Protection — Intensive MCQ Bank
1
What is the specific weight of water (commonly used in building calculations)?
A. 8.34 lb/gal
B. 1000 kg/m³
C. 62.4 lb/ft³ ✅
D. 9.81 N/kg
Rationale: The specific weight (weight per unit volume) of water is 62.4 pounds per cubic foot.
2
After a water test of a storm and sanitary system, what test is recommended to prove the system is gas
tight?
A. Hydrostatic test at 100 psi
B. Smoke pressure test at 1 in WC ✅
C. Vacuum test at -5 psi
D. Dye test with fluorescein
Rationale: A smoke pressure test (≈1 in. water column) is commonly used to detect gas/air leaks after
water testing.
3
Is an air test acceptable for storm and sanitary systems if a water test is not possible?
A. No — never acceptable
B. Yes — at 5 psi if water test is not possible ✅
C. Yes — at 1 psi only
D. Only for vertical stacks, never for horizontal lines
Rationale: Air testing at 5 psi is an accepted alternative when water testing cannot be performed.
4
,ESTUDYR
What is the usual water test procedure for storm and sanitary piping (before concealment)?
A. 1 ft WC for 1 hour
B. Minimum 10 ft WC (except topmost 10 ft), not to exceed 100 ft WC; plugs for >100 ft. ✅
C. 200 ft WC for entire system
D. Only peppermint oil test is required
Rationale: Standard procedure is 10 ft WC minimum (with limits and plug requirements as described).
5
Why is a peppermint oil test sometimes used on piping?
A. It measures structural strength
B. It sterilizes the pipe
C. To detect leaks by smell after boiling peppermint oil in water ✅
D. As a pressure gauge replacement
Rationale: Peppermint oil vapor can indicate leak locations by smell, though it’s hard to pinpoint leaks.
6
What is the maximum recommended dead-end length from a vent connection to any future drain outlet
to prevent slime/sludge growth?
A. 6 inches
B. 2 feet ✅
C. 10 feet
D. 8 feet
Rationale: A 2-ft maximum dead-end avoids stagnation and biological growth, except when extended to
an accessible cleanout.
7
Which fitting must not be used in a vertical drain run because of flow crossover and pressure issues?
A. Sanitary tee
B. Double sanitary tee ✅
C. Long-radius wye
D. Combination wye and 1/8 bend (tee-wye)
Rationale: Double sanitary tees can cause crossover flows and unstable pressure when one branch
discharges and another does not.
,ESTUDYR
8
What slope corresponds to ~2 fps velocity for 3-inch and smaller pipes?
A. 1/8 in/ft
B. 1/4 in/ft ✅
C. 1/2 in/ft
D. 1/16 in/ft
Rationale: For smaller pipes (≤3 in), 1/4 in/ft slope is used to maintain ~2 fps scouring velocity.
9
For larger pipes, what slope corresponds to ~2 fps?
A. 1/2 in/ft
B. 1/8 in/ft ✅
C. 1/4 in/ft
D. 1/16 in/ft
Rationale: Larger pipes require less slope; 1/8 in/ft is typical for 4–6 in.
10
Where should cleanouts be provided? (Select the best summary)
A. Only at the base of stacks
B. Only outside buildings
C. At exit point, every change >45°, every 50 ft (≤4"), every 100 ft (>4"), base of stacks, at direction
changes; manholes for >10" underground. ✅
D. Only on horizontal runs
Rationale: Multiple cleanouts are required for access: exits, directional changes, set intervals, stack
bases, and manholes for large underground mains.
11
What size of cleanout is required for piping up to 4 inches?
A. 2 inch cleanout
B. Same size as the pipe (i.e., full size) ✅
C. 6 inch cleanout
D. 1 inch cleanout
Rationale: For pipes ≤4", cleanout is usually the same diameter; for larger pipes, a 4" cleanout is
typically adequate.
, ESTUDYR
12
If there is danger of sewage backflow into a building, what should be installed?
A. A check valve only
B. A backwater valve (BWV) or BWV + manually operated gate valve ✅
C. A relief vent only
D. A sanitary tee
Rationale: BWV prevents backflow without interfering with airflow; a gate valve adds positive manual
protection where history of backflow exists.
13
Branch connections to the house drain should be made at the upper portion of the pipe (above half to
two-thirds full) because:
A. Easier to install fittings
B. Lower water temperature
C. Less stoppage risk, less flow interference, and more area available to relieve pneumatic pressure
fluctuations ✅
D. It reduces corrosion
Rationale: Upper-level taps reduce stoppage likelihood and prevent flow interference and pressure
issues.
14
How many fixture units (FUs) are equivalent to 1 gpm of continuous or semicontinuous flow?
A. 1 FU
B. 2 FUs ✅
C. 5 FUs
D. 0.5 FU
Rationale: 2 FUs corresponds to 1 gpm continuous (used for pumps, ejectors, HVAC condensate etc).
15
Minimum slopes for building drains to maintain scouring velocity: which is correct?
A. All pipes 1/16 in/ft
B. 3" and smaller 1/8 in/ft, larger 1/16 in/ft
C. 3" & smaller 1/4 in/ft; 4–6" 1/8 in/ft; ≥8" 1/16 in/ft (2 fps scouring) ✅
