Pipe Flow Velocity Chart

The best practice is a flow velocity of 3 ft./sec. or less. Flow rates up to 5 ft./sec. are possible for power generation. Flow rates over 5 ft./sec. are problematic and not a wise design criteria. The chart is for cast iron and thicker grades of pipe. Thinner or lower classes of pipe will be slower.

GPM 3/4″ 1″ 1.25″ 1.5″ 2″ 2.5″ 3″ 4″ 5″ 6″ 8″ 10″ 12″ 16″
1 0.72 0.41 0.26 0.18 0.1 0.07
2 1.4 0.82 0.52 0.36 0.2 0.13 0.09
3 2.2 1.2 0.78 0.55 0.31 0.19 0.14 0.08
4 2.9 1.6 1.04 0.73 0.41 0.26 0.18 0.11
5 3.6 2.0 1.3 0.9 0.51 0.32 0.23 0.13 0.08
6 4.3 2.4 1.56 1.1 0.61 0.39 0.27 0.16 0.1
7 5.1 2.9 1.82 1.25 0.71 0.45 0.32 0.18 0.12 0.08
8 5.8 3.3 2.1 1.45 0.82 0.52 0.36 0.21 0.13 0.09
10 7.2 4.1 2.6 1.8 1.0 0.65 0.45 0.25 0.16 0.11
12 4.9 3.1 2.2 1.2 0.78 0.5 0.31 0.20 0.13 0.08
14 5.7 3.6 2.5 1.4 0.9 0.6 0.36 0.23 0.16 0.09
16 6.5 4.2 2.9 1.6 1.0 0.7 0.40 0.26 0.18 0.1
18 7.3 4.7 3.3 1.8 1.2 0.8 0.45 0.29 0.2 0.11
20 8.2 5.2 3.6 2.0 1.3 0.9 0.51 0.33 0.23 0.13 0.08
25 6.5 4.6 2.5 1.65 1.15 0.64 0.41 0.28 0.16 0.1
30 7.8 5.4 3.1 1.9 1.4 0.77 0.48 0.34 0.19 0.12 0.08
35 9.1 6.3 3.6 2.3 1.6 0.9 0.56 0.4 0.22 0.14 0.1
40 10.4 7.2 4.1 2.6 1.8 1.03 0.64 0.45 0.26 0.16 0.11
45 8.2 4.6 2.9 2.0 1.16 0.73 0.5 0.29 0.18 0.12
50 9.1 5.1 3.3 2.3 1.3 0.83 0.55 0.32 0.2 0.14 0.08
55 10.0 5.6 3.6 2.5 1.43 0.92 0.62 0.35 0.22 0.16 0.88
60 10.9 6.1 3.9 2.7 1.56 1.0 0.68 0.38 0.24 0.17 0.96
70 12.7 7.1 4.6 3.2 1.81 1.15 0.79 0.45 0.29 0.2 0.11
75 7.7 4.9 3.4 1.93 1.22 0.85 0.48 0.31 0.21 0.12
80 8.2 5.2 3.6 2.06 1.3 0.91 0.51 0.33 0.23 0/13
90 9.2 5.9 4.1 2.31 1.48 1.0 0.58 0.37 0.26 0.14
100 10.2 6.5 4.5 2.5 1.62 1.1 0.65 0.41 0.28 0.16
125 12.7 8.1 5.7 3.2 2.02 1.4 0.81 0.51 0.35 0.2
150 9.8 6.9 3.8 2.43 1.7 0.97 0.61 0.42 0.24
175 11.4 7.9 4.5 2.83 2.0 1.14 0.71 0.49 0.28
200 13.1 9.0 5.1 3.28 2.3 1.3 0.82 0.57 0.32
225 10.1 5.75 3.66 2.55 1.45 0.91 0.64 0.36
250 11.3 6.4 4.04 2.8 1.6 1.01 0.71 0.4
300 13.6 7.7 4.96 3.4 1.9 1.2 0.85 0.48
350 9.0 5.7 4.0 2.2 1.4 0.98 0.56
400 10.2 6.4 4.5 2.6 1.6 1.1 0.65
450 11.5 7.2 5.1 2.9 1.8 1.25 0.73
500 12.8 8.0 5.7 3.3 2.0 1.4 0.8
600 9.6 6.8 3.8 2.4 1.7 0.96
700 11.6 7.9 4.5 2.9 2.0 1.1
800 13.2 9.1 5.1 3.3 2.3 1.3
900 10.2 5.8 3.7 2.6 1.4
1000 11.4 6.4 4.1 2.8 1.6
1100 12.4 7.0 4.5 3.1 1.8
1200 13.6 7.6 4.9 3.4 1.9
1400 9.0 5.7 4.0 2.2
1600 10.2 6.6 4.5 2.6
1800 11.4 7.2 5.1 2.9
2000 13.0 8.2 5.7 3.2
2500 10.1 7.1 4.0
3000 12.0 8.5 4.8
3500 9.8 5.6