ASPE CPD COMPREHENSIVE ANSWERS AND
QUESTIONS SET A+
✔✔Define ‚Äúindividual vent.‚Äù - ✔✔An individual vent vents one fixture only and is
seldom used unless the fixture is not part of a group.
✔✔Where should the vent be taken off from the horizontal drain pipe? - ✔✔Above the
centerline of the horizontal drain pipe. It should raise vertically or not more than 45
degrees from the vertical. The horizontal run of the vent should be at least 6 in above
the overflow level of the fixture.
✔✔What is the developed length of the vent pipe? - ✔✔The distance from the farthest
vented fixture of a group of fixtures to the roof outlet or vent stack or stack vent.
✔✔What is any connection from the vent stack called? - ✔✔Branch vent.
✔✔What is the exception to the ‚Äúone pipe diameter‚Äù slope of the vent opening and
the trap? - ✔✔Water closets and other similar fixtures
✔✔Why must the vent pipe opening never be below the weir of the fixture trap? - ✔✔A
fixture drain that slopes more than one pipe diameter between vent opening and trap
weir has a greater tendency to self siphon the trap seal than a fixture drain installed at a
slope of not more than one pipe diameter.
✔✔What is the maximum distance of vent to trap on a 2‚Äù plumbing line? - ✔✔60
inches, see table for other sizes.
✔✔Name the four alternate methods acceptable in lieu of individual trap venting. -
✔✔Wet venting Stack venting Circuit and Loop Venting Combination waste and vent
venting
✔✔Can a vent terminal be extended through a wall? How? What should you consider
for placement? - ✔✔Yes, but the terminal must turn down and be covered with a wire
,screen. It should never be located beneath a building overhang or immediately adjacent
to an exterior building wall.
✔✔Vent terminals should be how high above the roof level? - ✔✔6 inches, unless the
roof is used for other purposes, then it is at least 7 feet.
✔✔Vent terminals should not be located near what? Unless what? - ✔✔Within 10 feet
of any door, window, or ventilation intake unless they are extended at least 2ft above
such openings.
✔✔What is the size of the vent stack based on? What is it‚Äôs minimum size? - ✔✔The
size is based on drainage fixture unit load and the developed length. It should be not
less than one-half of the waste stack size.
✔✔Where are the three places the vent stack can terminate? - ✔✔The vent stack
should extend full size through the roof, connect to a vent header, or connect to the
stack vent of the drainage stack at least 6” above the overflow of the highest fixture.
✔✔Where is the most effective location for the vent stack? What is unique about this
location? - ✔✔Below all drainage branch connections and preferable at the top of the
horizontal drain immediately adjacent to the stack base fitting. This is the location where
pressure is at it’s maximum and the danger of closure due to fouling is at its
minimum.
✔✔What is the purpose of installing a vent stack? - ✔✔To prevent the development of
excessive pressures in the lower regions of the drainage stack by relieving the air as
rapidly as it is carried down the drainage stack.
✔✔How many branch intervals are permitted on a drainage stack for each attendant
vent stack, according to the CPD manual? - ✔✔Two, and up to five in some codes.
✔✔Can other things connect into the stack vent? - ✔✔The stack vent may be
connected with the vent stack before extending through the roof or may be connected
together with other stack vents or vent stacks in a vent header, and the vent header
may be extended through the roof as a single pipe.
✔✔Any connection to the vent stack is a _____? (various methods of fixture trap
venting) - ✔✔Branch vent.
✔✔Define Stack Vent - ✔✔The stack vent is the pipe from the topmost drainage branch
connection through the roof to atmosphere.
✔✔How is this circulation induced? - ✔✔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.
✔✔The principle of gravity circulation of air is utilized to keep the entire sanitary system
free of what? - ✔✔Foul odors, slime and fungi.
✔✔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‚Äôs the difference? - ✔✔The equivalent length.
✔✔At design conditions, how full is the drainage branch and what can be said about the
air in the pipe? - ✔✔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
✔✔How are the rates of air discharge for a pressure relief vent stack sized? -
✔✔Through tables.
✔✔Why is a vent stack provided in an area of high pressure (as water flows down the
stack and enters the horizontal drain)? - ✔✔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.
✔✔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? -
✔✔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.
✔✔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? - ✔✔24-Jul
✔✔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? - ✔✔The Darcy
Formula
✔✔What pressure variations must be sustained at the 2‚Äù fixture trap for 100% safety
factor? - ✔✔1‚Äù W.C.
✔✔How high is a column of air that is equivalent to the static pressure exerted by 1 in
water column? - ✔✔69.23 feet
QUESTIONS SET A+
✔✔Define ‚Äúindividual vent.‚Äù - ✔✔An individual vent vents one fixture only and is
seldom used unless the fixture is not part of a group.
✔✔Where should the vent be taken off from the horizontal drain pipe? - ✔✔Above the
centerline of the horizontal drain pipe. It should raise vertically or not more than 45
degrees from the vertical. The horizontal run of the vent should be at least 6 in above
the overflow level of the fixture.
✔✔What is the developed length of the vent pipe? - ✔✔The distance from the farthest
vented fixture of a group of fixtures to the roof outlet or vent stack or stack vent.
✔✔What is any connection from the vent stack called? - ✔✔Branch vent.
✔✔What is the exception to the ‚Äúone pipe diameter‚Äù slope of the vent opening and
the trap? - ✔✔Water closets and other similar fixtures
✔✔Why must the vent pipe opening never be below the weir of the fixture trap? - ✔✔A
fixture drain that slopes more than one pipe diameter between vent opening and trap
weir has a greater tendency to self siphon the trap seal than a fixture drain installed at a
slope of not more than one pipe diameter.
✔✔What is the maximum distance of vent to trap on a 2‚Äù plumbing line? - ✔✔60
inches, see table for other sizes.
✔✔Name the four alternate methods acceptable in lieu of individual trap venting. -
✔✔Wet venting Stack venting Circuit and Loop Venting Combination waste and vent
venting
✔✔Can a vent terminal be extended through a wall? How? What should you consider
for placement? - ✔✔Yes, but the terminal must turn down and be covered with a wire
,screen. It should never be located beneath a building overhang or immediately adjacent
to an exterior building wall.
✔✔Vent terminals should be how high above the roof level? - ✔✔6 inches, unless the
roof is used for other purposes, then it is at least 7 feet.
✔✔Vent terminals should not be located near what? Unless what? - ✔✔Within 10 feet
of any door, window, or ventilation intake unless they are extended at least 2ft above
such openings.
✔✔What is the size of the vent stack based on? What is it‚Äôs minimum size? - ✔✔The
size is based on drainage fixture unit load and the developed length. It should be not
less than one-half of the waste stack size.
✔✔Where are the three places the vent stack can terminate? - ✔✔The vent stack
should extend full size through the roof, connect to a vent header, or connect to the
stack vent of the drainage stack at least 6” above the overflow of the highest fixture.
✔✔Where is the most effective location for the vent stack? What is unique about this
location? - ✔✔Below all drainage branch connections and preferable at the top of the
horizontal drain immediately adjacent to the stack base fitting. This is the location where
pressure is at it’s maximum and the danger of closure due to fouling is at its
minimum.
✔✔What is the purpose of installing a vent stack? - ✔✔To prevent the development of
excessive pressures in the lower regions of the drainage stack by relieving the air as
rapidly as it is carried down the drainage stack.
✔✔How many branch intervals are permitted on a drainage stack for each attendant
vent stack, according to the CPD manual? - ✔✔Two, and up to five in some codes.
✔✔Can other things connect into the stack vent? - ✔✔The stack vent may be
connected with the vent stack before extending through the roof or may be connected
together with other stack vents or vent stacks in a vent header, and the vent header
may be extended through the roof as a single pipe.
✔✔Any connection to the vent stack is a _____? (various methods of fixture trap
venting) - ✔✔Branch vent.
✔✔Define Stack Vent - ✔✔The stack vent is the pipe from the topmost drainage branch
connection through the roof to atmosphere.
✔✔How is this circulation induced? - ✔✔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.
✔✔The principle of gravity circulation of air is utilized to keep the entire sanitary system
free of what? - ✔✔Foul odors, slime and fungi.
✔✔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‚Äôs the difference? - ✔✔The equivalent length.
✔✔At design conditions, how full is the drainage branch and what can be said about the
air in the pipe? - ✔✔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
✔✔How are the rates of air discharge for a pressure relief vent stack sized? -
✔✔Through tables.
✔✔Why is a vent stack provided in an area of high pressure (as water flows down the
stack and enters the horizontal drain)? - ✔✔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.
✔✔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? -
✔✔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.
✔✔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? - ✔✔24-Jul
✔✔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? - ✔✔The Darcy
Formula
✔✔What pressure variations must be sustained at the 2‚Äù fixture trap for 100% safety
factor? - ✔✔1‚Äù W.C.
✔✔How high is a column of air that is equivalent to the static pressure exerted by 1 in
water column? - ✔✔69.23 feet
