15. What pipe size in inches is
Fourth
requirement.
Multiple-
required to handle 400 gallons per
choice exercises 10 through 20 enable
minute at 1.5-percent slope?
you to show that you understand the
a. 6
c. 10
principles of sewage collection system
b. 8
d. 12
design.
16. For a flow of 1,000 gallons
10. No physical connections shall
per minute and a slope of 1
exist
between
sewer
and
water
percent, a pipe size of 12 inches
supply
systems.
What
minimum
is required.
What is the velocity
horizontal distance in feet is
in feet per second for this pipe
required between sewers and water
size and slope at full capacity?
lines?
a. 3.2
c. 4.1
a. 2
c. 4
b. 3.6
d. 4.4
b. 3
d. 5
17. For a flow of 500 gallons per
11. The second step in sewage
minute at a 2-percent slope, a pipe
collection system design is to
size of 8 inches is required (fig
locate manholes.
What is the only
14).
What will be the discharge
manhole
location
criterion
that
ratio?
cannot be exactly considered at
a. 0.623
c. 0.714
this point?
b. 0.690
d. 0.805
a. change in pipe size or slope
b. location of laterals
18. For a discharge ratio of 0.34
c. changes in pipe direction
and a full flow velocity of 5 feet
d. intersections of sewers
per second, what is the actual
velocity in feet per second?
12. What is the maximum flow rate
a. 3.5
c. 4.5
between manholes in gallons per
b. 4.0
d. 5.0
minute if the flow into the upper
manhole is 125 gallons per minute,
19. You are designing a sewer line
40 gallons per minute enter the
to connect a house with the main
line from a house connection, and
sewer.
The ground slope of 1.6
infiltration occurs at the rate of
feet in 80 feet is tried initially.
10 gallons per minute per 1,000
What will be the minimum pipe size
feet of pipe?
Assume the distance
in inches you can use for a maximum
between manholes to be 400 feet.
flow of 180 gallons per minute?
a. 153
c. 182
a. 6
c. 10
b. 169
d. 196
b. 8
d. 12
13. In
the
absence
of
other
20. You are designing a sewage
information, the peak sewage flow
collection system, and need the
from a TO facility can be assumed
elevation of a connection of a
to be what percentage of the peak
house line with the main.
If the
water demand?
next manhole upstream has an outlet
a. 65
c. 75
invert elevation of 390 feet and
b. 70
d. 80
the pipe slopes down at 2 percent,
what is the invert elevation in
14. Why is the natural ground
feet of the connection if it is 300
slope usually used as a first
feet downstream from the manhole?
estimate for a pipe slope?
a. 365
c. 378
a. facilitate excavation
b. 372
d. 384
b. control velocity
c. regulate drainage
d. prevent infiltration
4-26
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