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The carrying capacity of a given pipeline is limited by its internal resistance to the flow of water. This resistance to flow causes a loss of head or drip in pressure as the water moves through the line. The amount of head loss depends on (1) the velocity of the water, (2) the roughness of the interior surface of the pipe, (3) the internal diameter, and (4) the length of the line. These factors have been related in the widely used Hazen-Williams formula for computing head losses, pipe sizes, and carrying capacities in distribution lines. This formula is as follows: |
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Q = |
0.278 x C x D2.63 x S0.54 |
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in which: |
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Q = |
flow of water through the pipe in cubic meters per second |
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C = |
factor depending on the roughness of the interior surface |
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D = |
pipe diameter in meters |
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S = |
hydraulic slope or head loss in meters per meter of pipe |
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The factor "C" is well known as the Hazen-Williams "C" or flow coefficient "C," and its value must be estimated in flow calculations. Numerous tests have shown that cement-lined pipe installed many years ago maintains a "C" of approximately 140 to 150, even in tuberculating waters. The quality of more recent, high-speed ACIPCO cement linings, and the availability of even larger pipe sizes, may justify the use of the higher values for "C," particularly in intermediate and larger pipe sizes.
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| Hazen-Williams "C" = 145* | |
Flow of Water in Ductile Iron Pipe TABLE 1
Flow in
Liters per
Second |
100mm Class K9 Pipe |
150mm Class K9 Pipe |
200mm Class K9 Pipe |
250mm Class K9 Pipe |
300mm Class K9 Pipe |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
| 1 |
0.13 |
0.22 |
|
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|
|
|
|
|
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| 2 |
0.26 |
0.81 |
|
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|
|
|
|
|
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| 3 |
0.38 |
1.71 |
0.17 |
0.22 |
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|
|
|
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| 4 |
0.51 |
2.91 |
0.22 |
0.38 |
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|
|
|
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| 5 |
0.64 |
4.39 |
0.28 |
0.58 |
0.15 |
0.14 |
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|
|
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| 10 |
1.28 |
15.84 |
0.56 |
2.08 |
0.31 |
0.50 |
0.20 |
0.17 |
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| 15 |
1.92 |
33.53 |
0.83 |
4.41 |
0.46 |
1.05 |
0.30 |
0.35 |
0.20 |
0.14 |
| 20 |
2.56 |
57.10 |
1.11 |
7.52 |
0.62 |
1.80 |
0.39 |
0.60 |
0.27 |
0.25 |
| 25 |
3.2 |
86.28 |
1.39 |
11.36 |
0.77 |
2.71 |
0.49 |
0.91 |
0.34 |
0.37 |
| 30 |
|
|
1.67 |
15.91 |
0.93 |
3.80 |
0.59 |
1.27 |
0.41 |
0.52 |
| 40 |
|
|
2.22 |
27.10 |
1.23 |
6.47 |
0.79 |
2.17 |
0.55 |
0.89 |
| 50 |
|
|
2.78 |
40.94 |
1.54 |
9.78 |
0.98 |
3.28 |
0.68 |
1.34 |
| 60 |
|
|
3.33 |
57.37 |
1.85 |
13.70 |
1.18 |
4.59 |
0.82 |
1.88 |
| 70 |
|
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2.16 |
18.23 |
1.38 |
6.11 |
0.95 |
2.50 |
| 80 |
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2.47 |
23.33 |
1.57 |
7.82 |
1.09 |
3.20 |
| 90 |
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2.78 |
29.02 |
1.77 |
9.72 |
1.23 |
3.98 |
| 100 |
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3.08 |
35.26 |
1.97 |
11.82 |
1.36 |
4.84 |
| 120 |
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2.36 |
16.55 |
1.64 |
6.78 |
| 140 |
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2.75 |
22.02 |
1.91 |
9.02 |
| 160 |
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3.15 |
28.19 |
2.18 |
11.55 |
| 180 |
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2.45 |
14.36 |
| 200 |
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2.73 |
17.45 |
| 250 |
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3.41 |
26.37 |
| 300 |
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4.09 |
36.95 |
Notes:
Loss of head shown is per 1000m of pipeline.
Table is based on minimum class, cement-lined ductile iron pipe.
* The Hazen-Williams flow coefficient shown is a representative value for long-term service of cement-mortar-lined ductile iron pipe. Values of C=140 to C=155 have been used by various manufacturers as a long-term Hazen-Williams coefficient, depending on pipe diameter and lining smoothness. The design of systems outside common water velocities, i.e. 0.5m/s to 1.5m/s, may involve special design considerations (for example, the generation of substantial surge pressures as a result of valve closure or other water column effects, sedimentation at extremely low velocities, etc.)
Flow of Water in Ductile Iron Pipe TABLE 2
Flow in
Liters per
Second |
350mm Class K9 Pipe |
400mm Class K9 Pipe |
450mm Class K8 Pipe |
500mm Class K8 Pipe |
600mm Class K7 Pipe |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
| 20 |
0.20 |
0.12 |
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| 30 |
0.31 |
0.26 |
0.24 |
0.14 |
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| 40 |
0.41 |
0.44 |
0.31 |
0.23 |
0.25 |
0.13 |
0.20 |
0.08 |
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| 50 |
0.51 |
0.67 |
0.39 |
0.35 |
0.31 |
0.19 |
0.25 |
0.12 |
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| 60 |
0.61 |
0.94 |
0.47 |
0.49 |
0.37 |
0.27 |
0.30 |
0.16 |
0.21 |
0.07 |
| 70 |
0.72 |
1.25 |
0.55 |
0.65 |
0.43 |
0.36 |
0.35 |
0.22 |
0.24 |
0.09 |
| 80 |
0.82 |
1.60 |
0.63 |
0.84 |
0.49 |
0.46 |
0.40 |
0.28 |
0.27 |
0.11 |
| 90 |
0.92 |
1.99 |
0.71 |
1.04 |
0.55 |
0.58 |
0.45 |
0.34 |
0.31 |
0.14 |
| 100 |
1.02 |
2.41 |
0.78 |
1.26 |
0.62 |
0.70 |
0.50 |
0.42 |
0.34 |
0.17 |
| 120 |
1.23 |
3.38 |
0.94 |
1.77 |
0.74 |
0.98 |
0.60 |
0.58 |
0.41 |
0.24 |
| 140 |
1.43 |
4.5 |
1.10 |
2.35 |
0.86 |
1.30 |
0.70 |
0.78 |
0.48 |
0.31 |
| 160 |
1.64 |
5.76 |
1.26 |
3.01 |
0.98 |
1.67 |
0.80 |
0.99 |
0.55 |
0.40 |
| 180 |
1.84 |
7.16 |
1.41 |
3.75 |
1.11 |
2.08 |
0.90 |
1.24 |
0.62 |
0.50 |
| 200 |
2.05 |
8.70 |
1.57 |
4.55 |
1.23 |
2.52 |
0.99 |
1.50 |
0.69 |
0.61 |
| 250 |
2.56 |
13.15 |
1.96 |
6.88 |
1.54 |
3.81 |
1.24 |
2.27 |
0.86 |
0.92 |
| 300 |
3.07 |
18.42 |
2.35 |
9.64 |
1.85 |
5.34 |
1.49 |
3.18 |
1.03 |
1.28 |
| 350 |
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2.75 |
12.82 |
2.15 |
7.10 |
1.74 |
4.23 |
1.20 |
1.71 |
| 400 |
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3.14 |
16.41 |
2.46 |
9.09 |
1.99 |
5.41 |
1.37 |
2.19 |
| 450 |
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2.77 |
11.31 |
2.24 |
6.73 |
1.54 |
2.72 |
| 500 |
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3.08 |
13.74 |
2.49 |
8.18 |
1.71 |
3.30 |
| 600 |
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2.98 |
11.46 |
2.06 |
4.63 |
| 700 |
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2.40 |
6.16 |
| 800 |
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2.74 |
7.88 |
| 900 |
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3.08 |
9.8 |
| 1000 |
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3.43 |
11.91 |
Notes:
Loss of head shown is per 1000m of pipeline.
Table is based on minimum class, cement-lined ductile iron pipe.
* The Hazen-Williams flow coefficient shown is a representative value for long-term service of cement-mortar-lined ductile iron pipe. Values of C=140 to C=155 have been used by various manufacturers as a long-term Hazen-Williams coefficient, depending on pipe diameter and lining smoothness. The design of systems outside common water velocities, i.e. 0.5m/s to 1.5m/s, may involve special design considerations (for example, the generation of substantial surge pressures as a result of valve closure or other water column effects, sedimentation at extremely low velocities, etc.)
Flow of Water in Ductile Iron Pipe TABLE 3
Flow in
Liters per
Second |
700mm Class K7 |
800mm Class K7 |
900mm Class K7 |
1000mm Class K7 |
1200mm Class K7 |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
| 100 |
0.25 |
0.08 |
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| 150 |
0.38 |
0.17 |
0.29 |
0.09 |
0.23 |
0.05 |
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| 200 |
0.51 |
0.29 |
0.39 |
0.15 |
0.31 |
0.08 |
0.25 |
0.05 |
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| 250 |
0.63 |
0.44 |
0.48 |
0.23 |
0.38 |
0.13 |
0.31 |
0.08 |
0.21 |
0.03 |
| 300 |
0.76 |
0.61 |
0.58 |
0.32 |
0.46 |
0.18 |
0.37 |
0.11 |
0.26 |
0.04 |
| 350 |
0.89 |
0.82 |
0.68 |
0.42 |
0.53 |
0.24 |
0.43 |
0.14 |
0.30 |
0.06 |
| 400 |
1.01 |
1.05 |
0.77 |
0.54 |
0.61 |
0.31 |
0.49 |
0.18 |
0.34 |
0.07 |
| 450 |
1.14 |
1.30 |
0.87 |
0.67 |
0.69 |
0.38 |
0.56 |
0.23 |
0.39 |
0.09 |
| 500 |
1.27 |
1.58 |
0.97 |
0.82 |
0.76 |
0.46 |
0.62 |
0.28 |
0.43 |
0.11 |
| 600 |
1.52 |
2.22 |
1.16 |
1.15 |
0.92 |
0.65 |
0.74 |
0.39 |
0.51 |
0.16 |
| 700 |
1.77 |
2.95 |
1.35 |
1.53 |
1.07 |
0.86 |
0.87 |
0.52 |
0.60 |
0.21 |
| 800 |
2.03 |
3.77 |
1.55 |
1.96 |
1.22 |
1.10 |
0.99 |
0.66 |
0.69 |
0.27 |
| 900 |
2.28 |
4.69 |
1.74 |
2.43 |
1.37 |
1.37 |
1.11 |
0.82 |
0.77 |
0.34 |
| 1000 |
2.53 |
5.70 |
1.93 |
2.96 |
1.53 |
1.66 |
1.24 |
1.00 |
0.86 |
0.41 |
| 1200 |
3.04 |
7.99 |
2.32 |
4.14 |
1.83 |
2.33 |
1.48 |
1.40 |
1.03 |
0.57 |
| 1400 |
|
|
2.7 |
5.51 |
2.14 |
3.10 |
1.73 |
1.86 |
1.20 |
0.76 |
| 1600 |
|
|
3.09 |
7.05 |
2.44 |
3.97 |
1.98 |
2.38 |
1.37 |
0.97 |
| 1800 |
|
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|
2.75 |
4.94 |
2.22 |
2.96 |
1.54 |
1.21 |
| 2000 |
|
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|
3.05 |
6.00 |
2.47 |
3.59 |
1.71 |
1.47 |
| 2200 |
|
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|
2.72 |
4.29 |
1.88 |
1.76 |
| 2400 |
|
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|
2.97 |
5.03 |
2.06 |
2.06 |
| 2600 |
|
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3.21 |
5.84 |
2.23 |
2.39 |
| 2800 |
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2.40 |
2.74 |
| 3000 |
|
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2.57 |
3.12 |
| 3500 |
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3.00 |
4.15 |
| 4000 |
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3.43 |
5.31 |
Notes:
Loss of head shown is per 1000m of pipeline.
Table is based on minimum class, cement-lined ductile iron pipe.
* The Hazen-Williams flow coefficient shown is a representative value for long-term service of cement-mortar-lined ductile iron pipe. Values of C=140 to C=155 have been used by various manufacturers as a long-term Hazen-Williams coefficient, depending on pipe diameter and lining smoothness. The design of systems outside common water velocities, i.e. 0.5m/s to 1.5m/s, may involve special design considerations (for example, the generation of substantial surge pressures as a result of valve closure or other water column effects, sedimentation at extremely low velocities, etc.)
Flow of Water in Ductile Iron Pipe TABLE 4
Flow in
Liters per
Second |
1400mm Class K7 Pipe |
1500mm Class K7 Pipe |
1600mm Class K7 Pipe |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
Velocity
in Meters
per Sec. |
Loss of
Head (m) |
| 400 |
0.25 |
0.04 |
0.22 |
0.03 |
|
|
| 500 |
0.32 |
0.05 |
0.28 |
0.04 |
0.24 |
0.03 |
| 600 |
0.38 |
0.08 |
0.33 |
0.05 |
0.29 |
0.04 |
| 700 |
0.44 |
0.10 |
0.39 |
0.07 |
0.34 |
0.05 |
| 800 |
0.51 |
0.13 |
0.44 |
0.09 |
0.39 |
0.07 |
| 900 |
0.57 |
0.16 |
0.50 |
0.12 |
0.44 |
0.08 |
| 1000 |
0.63 |
0.20 |
0.55 |
0.14 |
0.48 |
0.10 |
| 1200 |
0.76 |
0.28 |
0.66 |
0.20 |
0.58 |
0.14 |
| 1400 |
0.89 |
0.37 |
0.77 |
0.26 |
0.68 |
0.19 |
| 1600 |
1.01 |
0.47 |
0.88 |
0.33 |
0.78 |
0.24 |
| 1800 |
1.14 |
0.58 |
0.99 |
0.42 |
0.87 |
0.30 |
| 2000 |
1.27 |
0.71 |
1.10 |
0.51 |
0.97 |
0.37 |
| 2500 |
1.58 |
1.07 |
1.38 |
0.76 |
1.21 |
0.56 |
| 3000 |
1.90 |
1.50 |
1.66 |
1.07 |
1.45 |
0.78 |
| 3500 |
2.22 |
1.99 |
1.93 |
1.42 |
1.70 |
1.04 |
| 4000 |
2.54 |
2.55 |
2.21 |
1.82 |
1.94 |
1.33 |
| 4500 |
2.85 |
3.17 |
2.48 |
2.26 |
2.18 |
1.65 |
| 5000 |
3.17 |
3.85 |
2.76 |
2.75 |
2.42 |
2.01 |
| 5500 |
|
|
3.03 |
3.28 |
2.67 |
2.40 |
| 6000 |
|
|
|
|
2.91 |
2.81 |
| 6500 |
|
|
|
|
3.15 |
3.26 |
| 7000 |
|
|
|
|
3.39 |
3.74 |
Notes:
Loss of head shown is per 1000m of pipeline.
Table is based on minimum class, cement-lined ductile iron pipe.
* The Hazen-Williams flow coefficient shown is a representative value for long-term service of cement-mortar-lined ductile iron pipe. Values of C=140 to C=155 have been used by various manufacturers as a long-term Hazen-Williams coefficient, depending on pipe diameter and lining smoothness. The design of systems outside common water velocities, i.e. 0.5m/s to 1.5m/s, may involve special design considerations (for example, the generation of substantial surge pressures as a result of valve closure or other water column effects, sedimentation at extremely low velocities, etc.)
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