Environmental Engineering Reference
In-Depth Information
Table 3-3
Trajectory needed to achieve flushing velocity
Diameter
of Main
Diameter,
d
,
of Discharge
Tr a j e c t o r y (
Sx
)
for 1
ft/sec
Trajectory (
Sx
)
for 2.5
ft/sec
in
.
mm
in
.
mm
ft
m
ft
m
6
152
2
.0
51
4
.0
1.2
8.8
2.7
6
152
2.5
64
2.5
0.8
5.7
1.7
6
152
4
.0
102
1
.0
0.3
2.2
0.7
8
203
2
.0
51
6.6
2
.0
17.7
5.4
8
203
2.5
64
4.2
1.3
11.3
3.5
8
203
3
.0
76
3
.0
0.9
7.9
2.4
8
203
4
.0
102
1.7
0.5
4.4
1.3
N
OTE
: 36 in. (914 mm) distance from discharge to ground (
Sy
in Figure 3-3)
Table
Tamer
This table lists some typical results when using the
trajectory discharge method and the equation shown in
Figure 3-3. The table assumes that the distance from
discharge to the ground (
Sy
) is 36 in. The calculation is
provided so that
only
the trajectory distance from the
discharge pipe is needed. Example: A 6-in. main is flushed
using a 2.5-in. diameter discharge pipe. To achieve a
2.5 ft/sec velocity in the main, the trajectory must be 5.7 ft.
should be followed with an application of chlorine solution as pre-
viously described.
More aggressive methods of cleaning larger diameter pipe-
lines include using powerwashers or hydraulic spray jets. The
equipment, used commonly for cleaning sewer collection system
piping, is suitable for this purpose (Figure 3-7, 3-8). These
devices may be self-propelled and can do a superior job cleaning
the pipe interior. Some high pressure powerwashers can clean an
entire pipe section from one end.
Preventing Backflow During Installation
High chlorine levels used for disinfection of new pipelines
or other nonpotable conditions may contaminate the potable
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