ASPE CPD STUDY 2025
QUESTIONS AH
ANSWER ALL QUESTIONS IN THIS SECTION
QUESTION 1
Any connection to the vent stack is a _____? (various methods of fixture trap
venting) - ANSWERS-Branch vent.
QUESTION 2
Define Stack Vent - ANSWERS-The stack vent is the pipe from the topmost
drainage branch connection through the roof to atmosphere.
QUESTION 3
How is this circulation induced? - ANSWERS-The circulation is induced by the
difference in head pressure between outdoor air and the air in the vent piping. This
difference in head pressure is due to the difference in temperature and thus the
difference in density of each air source and the height of the air column in the vent
piping. The cool air, being more dense, displaces the less cool air and circulation is
induced.
END OF
PAGE 1
, ASPE CPD STUDY 2025
QUESTIONS AH
QUESTION 4
The principle of gravity circulation of air is utilized to keep the entire sanitary
system free of what? - ANSWERS-Foul odors, slime and fungi.
QUESTION 5
What is the maximum length of vent piping for any particular size with a
maximum allowable pressure drop of 1 in w.c.: the developed length or the
equivalent length? What’s the difference? - ANSWERS-The equivalent length.
QUESTION 6
At design conditions, how full is the drainage branch and what can be said about
the air in the pipe? - ANSWERS-it is assumed that the drainage branch flows half-
full at design conditions and that the air in the upper half of the pipe flows at the
same velocity and capacity
QUESTION 7
How are the rates of air discharge for a pressure relief vent stack sized? -
ANSWERS-Through tables.
END OF
PAGE 2
, ASPE CPD STUDY 2025
QUESTIONS AH
QUESTION 8
Why is a vent stack provided in an area of high pressure (as water flows down the
stack and enters the horizontal drain)? - ANSWERS-This is the area where
hydraulic jump occurs. A vent stack is provided in this area of high pressure to
provide an avenue for the flow of air to relieve the high pressure.
QUESTION 9
Why must stacks be extended full size through the roof, and why may soil stacks
not be reduced in size even though there is less load on the upper portions of the
stack? - ANSWERS-As water falls down the stack, it exerts frictional drag on the
core of air and as this air is dragged down, it must be replaced by an equivalent
quantity of replacement air to avoid violent pressure fluctuations.
QUESTION 10
At maximum design flow, water flows down the stack as a sheet of water
occupying how much of the cross sectional area of the stack? - ANSWERS-24-Jul
QUESTION 11
END OF
PAGE 3
, ASPE CPD STUDY 2025
QUESTIONS AH
When air flows in a pipe, a pressure loss occurs due to the friction between the air
and the pipe wall. This loss of pressure is expressed by which formula? -
ANSWERS-The Darcy Formula
QUESTION 12
What pressure variations must be sustained at the 2” fixture trap for 100% safety
factor? - ANSWERS-1” W.C.
QUESTION 13
How high is a column of air that is equivalent to the static pressure exerted by 1 in
water column? - ANSWERS-69.23 feet
QUESTION 14
Design wise, what three things should one consider when placing a backflow
prevention device? - ANSWERS-1. all backflow prevention devices have a high
pressure drop that the design must compensate. 2. good plumbing design is to add
a strainer upstream of the backflow device to prevent debris from obstructing the
check valves 3. if using a reduced-pressure backflow device, these have a high
relief discharge rate, which must be accommodated
END OF
PAGE 4
QUESTIONS AH
ANSWER ALL QUESTIONS IN THIS SECTION
QUESTION 1
Any connection to the vent stack is a _____? (various methods of fixture trap
venting) - ANSWERS-Branch vent.
QUESTION 2
Define Stack Vent - ANSWERS-The stack vent is the pipe from the topmost
drainage branch connection through the roof to atmosphere.
QUESTION 3
How is this circulation induced? - ANSWERS-The circulation is induced by the
difference in head pressure between outdoor air and the air in the vent piping. This
difference in head pressure is due to the difference in temperature and thus the
difference in density of each air source and the height of the air column in the vent
piping. The cool air, being more dense, displaces the less cool air and circulation is
induced.
END OF
PAGE 1
, ASPE CPD STUDY 2025
QUESTIONS AH
QUESTION 4
The principle of gravity circulation of air is utilized to keep the entire sanitary
system free of what? - ANSWERS-Foul odors, slime and fungi.
QUESTION 5
What is the maximum length of vent piping for any particular size with a
maximum allowable pressure drop of 1 in w.c.: the developed length or the
equivalent length? What’s the difference? - ANSWERS-The equivalent length.
QUESTION 6
At design conditions, how full is the drainage branch and what can be said about
the air in the pipe? - ANSWERS-it is assumed that the drainage branch flows half-
full at design conditions and that the air in the upper half of the pipe flows at the
same velocity and capacity
QUESTION 7
How are the rates of air discharge for a pressure relief vent stack sized? -
ANSWERS-Through tables.
END OF
PAGE 2
, ASPE CPD STUDY 2025
QUESTIONS AH
QUESTION 8
Why is a vent stack provided in an area of high pressure (as water flows down the
stack and enters the horizontal drain)? - ANSWERS-This is the area where
hydraulic jump occurs. A vent stack is provided in this area of high pressure to
provide an avenue for the flow of air to relieve the high pressure.
QUESTION 9
Why must stacks be extended full size through the roof, and why may soil stacks
not be reduced in size even though there is less load on the upper portions of the
stack? - ANSWERS-As water falls down the stack, it exerts frictional drag on the
core of air and as this air is dragged down, it must be replaced by an equivalent
quantity of replacement air to avoid violent pressure fluctuations.
QUESTION 10
At maximum design flow, water flows down the stack as a sheet of water
occupying how much of the cross sectional area of the stack? - ANSWERS-24-Jul
QUESTION 11
END OF
PAGE 3
, ASPE CPD STUDY 2025
QUESTIONS AH
When air flows in a pipe, a pressure loss occurs due to the friction between the air
and the pipe wall. This loss of pressure is expressed by which formula? -
ANSWERS-The Darcy Formula
QUESTION 12
What pressure variations must be sustained at the 2” fixture trap for 100% safety
factor? - ANSWERS-1” W.C.
QUESTION 13
How high is a column of air that is equivalent to the static pressure exerted by 1 in
water column? - ANSWERS-69.23 feet
QUESTION 14
Design wise, what three things should one consider when placing a backflow
prevention device? - ANSWERS-1. all backflow prevention devices have a high
pressure drop that the design must compensate. 2. good plumbing design is to add
a strainer upstream of the backflow device to prevent debris from obstructing the
check valves 3. if using a reduced-pressure backflow device, these have a high
relief discharge rate, which must be accommodated
END OF
PAGE 4
