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ASPE CPD Study Questions AH
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ASPE CPD Study Questions AHA centrifugal pump always operates at what condition? - ANS-The intersection of its
head/capacity curve and the system head/capacity curve.
A drainage stack should never be designed for a capacity greater than what and why? -
ANS-One-thrid full, because the pressure fluctuations in the system could greatly
exceed the maximum 1 in water column criterion and lose their seal by siphonage
blowout
A sanitary tee may be used in the vertical but what may not be used in the vertical and
why? - ANS-A double sanitary tee because the possibility of flow crossover and
excessive pressures when one branch is discharging and the other isn’t are possible
A sump handles what? - ANS-Clear waste water (sump basin not airtight, needs no
venting)
An ejector handles what? - ANS-Sewage (ejector basin is airtight and requires venting)
Any connection to the vent stack is a _____? (various methods of fixture trap venting) -
ANS-Branch vent.
Any offset of the stack greater than what can cause hydraulic jump? - ANS-45 degrees
Are site drainage slope requirements steeper or shallower than building plumbing slope
requirements? - ANS-Shallower.
Are suds more or less dense than air? - ANS-More dense, 2 to 19 lb/ft^3 depending on
the detergent.
Are vertical walls included in the calculation for stormwater runoff? - ANS-Some codes
require 50 percent of the area of vertical walls be added to the horizontal drained area.
Some do not.
At 4 in/hr rainfall, roughly how much area will result in 1 gpm of rainfall? - ANS-24 sq.ft
To apply this for other rates of rainfall, multiply (24x4) and divide by the new rate. (There
should be tables for this in all plumbing codes)
,At design conditions, how full is the drainage branch and what can be said about the air
in the pipe? - ANS-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
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? - ANS-24-Jul
Before commencing design of the system, the engineer should contact the local utility
company to determine what? - ANS-Their rules and regulations, the point at which the
utility company’s work ends and the contractors work begins, BTU value and
pressure of gas supplied, any special requirements
Branch connections to the house drain should be made where and why? - ANS-At the
upper portion of the pipe (above the 1/2 - 2/3 full mark) because: 1) there is a lower
chance of stoppages in the branch 2) there is less flow interference at the point of
connection 3) When there is no flow in the branch, the full area of the pipe is available
to relieve pneumatic pressure fluctuations in the house drain
By what method does hot water supply piping (whether insulated or not) transfer heat to
surrounding lower-temperature air? - ANS-Convection, conduction, and radiation.
Can a vent terminal be extended through a wall? How? What should you consider for
placement? - ANS-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.
Can other things connect into the stack vent? - ANS-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.
Define “Coefficient of Expansion” - ANS-The unit increase in length of a material
per 1 degree F increase in temperature
Define “common vent.” - ANS-A vent for two trapped fixtures on the same floor
level (connecting to a common vertical drain), or a horizontal branch drain for two wall
outlet fixtures. Keep in mind the maximum distance from the trap to the vent.
,Define “individual vent.” - ANS-An individual vent vents one fixture only and is
seldom used unless the fixture is not part of a group.
Define “vapor pressure” - ANS-The pressure a liquid exert on its surroundings (this
varies directly with temperature)
Define Maximum Flow, Average Flow, and Maximum Probable Flow: - ANS-The flow
that will occur if the outlets on all of the fixtures are opened simultaneously (maximum
possible flow). The flow that is likely to occur in the piping under normal conditions. The
maximum flow that will occur in the piping under peak conditions (peak demand or peak
flow).
Define Stack Vent - ANS-The stack vent is the pipe from the topmost drainage branch
connection through the roof to atmosphere.
Define Stormwater: - ANS-Rainwater, surface runoff, ground water, subsurface water, or
similar clear liquid wastes, exclusive of sewage, condensate, and industrial waste
Define velocity head. - ANS-Velocity head (V^2 over 2g) is a measure of the decrease in
static pressure head experienced in feet of water column.
Describe “circuit vent” - ANS-A circuit vent may be used for a maximum of 8
fixtures. All fixtures must connect horizontally to the horizontal branch drain being circuit
vented, and the connection shall be between the two most upstream fixture drains. It
shall be a dry vent sized for all DFUs of the drain. If there are four or more water
closets, provide a relief vent, which shall be the same size as the circuit vent and may
be a wet vent. This drain line of the circuit vent must be full size for the entire length of
run.
Describe “combination drain and vent” - ANS-This serves a drain line that has
horizontal branches, and no food waste grinders or chemical sinks can be included.
This pipe carries air and water, and in some codes, the permitted sizes are one size
more than the calculated drain size. (Other codes use a table).
Describe “horizontal wet venting” - ANS-This method is used for bathroom groups
of fixtures in one or two bathrooms where the fixture drains are in a row and not one
above the other. This common vent and waste pipe will be larger, so look for a special
table. In some cases a relief vent will be required.
, Describe “waste stack vent” - ANS-The waste stack in this case acts as the waste
stack and vent. No offsets, water closets or urinals are included, each fixture connects
separately, and fixtures must be of the same type. Some codes limit this arrangement to
three floors. This has special sizing tables and the stack shall be the same size for its
entire length.
Describe “wet venting” or “vertical wet venting” - ANS-Another form of
common venting where one fixture is above the other. In this case, the pipe between the
fixtures carries both waste and air. Where this occurs, always look for a larger pipe size
in the code or a special table. The upper fixture cannot be a water closet or urinal.
Describe a Barometric Loop. - ANS-In backflow prevention, a barometric loop is a piping
arrangement based on the principle that atmospheric pressure cannot raise a column of
water more than approximately 34 feet even when it is subject to a perfect vacuum. The
piping arrangement is formed by constructing a loop in the potable water supply line that
rises 35 feet or more above the highest point of a nonpotable system This is effective
against back siphonage only and should never be used where back pressure is
available.
Describe a double check valve assembly. - ANS-This consists of two independently
acting, internally loaded check valves. It is effective against backflow caused by either
back pressure or back siphonage. The complete assembly includes two shutoff valves,
a strainer, and test cocks for field testing. There is no provision for discharging water
and there is no visual indication of backflow or unit malfunction. Not as effective as
reduced-pressure devices so rarely used. For low hazard uses.
Describe a pressure vacuum breaker. - ANS-A device consisting of one or two positive
seating check valves and an internally spring loaded, disc-float assembly installed as a
unit between two shutoff valves and fitted with properly located test cocks. The
disc-float is spring loaded to allow air to enter the system when the line pressure drops
to 1 psi or lower. These are similar to atmospheric vacuum breakers except they can be
used under continuous pressure. These are for back siphonage only, and are not to be
used for backflow due to pressure. They should be installed a minimum of 12 in above
the highest point of use.
Describe a reduced pressure backflow device. - ANS-An assembly consisting of two
independently acting, internally loaded check valves separated by a reduced-pressure
zone. A differential pressure relief valve is located within the reduced pressure zone to
maintain the reduced pressure and to discharge water to the atmosphere in the event of
device malfunction. Typical use is where the nonpotable water source is considered to
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