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Selection & Sizing

Suction Pipe Diameter Selection

Last updated: December 2, 2024

Here’s a simplified Remko suction sizing chart based on common practice of keeping suction velocity ≤ 1.5 m/s (design 1.0-1.2 m/s for quiet, cavitation-safe operation).

Selection Rule

Pick the next pipe size up whose “Design (1.2 m/s)” capacity is ≥ your duty flow.

Remko Suction Pipe Quick-Select

Flows at listed velocities (L/s / m³/h)

DN (mm) Design-Quiet 1.0 m/s Design 1.2 m/s Upper Limit 1.5 m/s
50 2 / 7 2 / 8 3 / 11
75 4 / 16 5 / 19 7 / 24
100 8 / 28 9 / 34 12 / 42
150 18 / 64 21 / 76 27 / 95
200 31 / 113 38 / 136 47 / 170
250 49 / 177 59 / 212 74 / 265
300 71 / 254 85 / 305 106 / 382
350 96 / 346 115 / 416 144 / 520
400 126 / 452 151 / 543 188 / 679
450 159 / 573 191 / 687 239 / 859
500 196 / 707 236 / 848 295 / 1,060
600 283 / 1,018 339 / 1,221 424 / 1,527
700 385 / 1,385 462 / 1,663 577 / 2,078
750 442 / 1,590 530 / 1,909 663 / 2,386
800 503 / 1,810 603 / 2,171 754 / 2,714
900 636 / 2,290 763 / 2,748 954 / 3,435

How to Use

1

Find Duty Flow

Take your duty flow (L/s or m³/h).

2

Select DN

Choose the DN where the Design 1.2 m/s column meets or exceeds your flow.

3

Size Up If Needed

If suction run is long, has many fittings, poor NPSH margin, or viscous fluid, size up one DN (aim for ~1.0 m/s).

Good Practice

Use an eccentric reducer (flat on top) at the pump nozzle

Keep suction piping short, straight, and oversized; minimize elbows/valves before the pump

Install a straight length ≥ 5x pipe OD into the pump (more if using a strainer or elbow at the inlet)

For self-priming/auto-prime sets, ensure airtight suction and foot/check arrangements per the priming system used

Engineering Use

Suction Lines

Keep velocity ≤ 1.5 m/s (ideally 1.0 m/s for long runs or poor NPSH conditions)

Discharge Lines

Velocity can be 2.5-3.0 m/s safely

Example Calculation

Given: Flow = 360 m³/h (100 L/s)

200 mm (8″) pipe:

Velocity = 1.8 m/s

Slightly above suction limit, fine for discharge

250 mm (10″) pipe:

Velocity = 1.14 m/s

Better suction choice

Complete Velocity Reference Table

This comprehensive table shows suction line velocities (m/s) for different pipe sizes across a wide range of flow rates. Use this to verify your pipe selection results in acceptable flow velocities.

Green: Safe (≤ 1.5 m/s)
Yellow: Borderline (1.6 – 2.5 m/s)
Orange: High (2.5 – 4.0 m/s)
Red: Too High (> 4.0 m/s)

68 flow rates from 2 L/s to 800 L/s | 11 pipe sizes from 2″ (DN50) to 20″ (DN500)

L/s 2″ 3″ 4″ 6″ 8″ 10″ 12″ 14″ 16″ 18″ 20″
DN50 DN75 DN100 DN150 DN200 DN250 DN300 DN350 DN400 DN450 DN500
2 1.02 0.45 0.25 0.11 0.06 0.04 0.03 0.02 0.02 0.01 0.01
4 2.04 0.91 0.51 0.23 0.13 0.08 0.06 0.04 0.03 0.03 0.02
6 3.06 1.36 0.76 0.34 0.19 0.12 0.08 0.06 0.05 0.04 0.03
8 4.07 1.81 1.02 0.45 0.25 0.16 0.11 0.08 0.06 0.05 0.04
10 5.09 2.26 1.27 0.57 0.32 0.20 0.14 0.10 0.08 0.06 0.05
12 6.11 2.72 1.53 0.68 0.38 0.24 0.17 0.12 0.10 0.08 0.06
14 7.13 3.17 1.78 0.79 0.45 0.29 0.20 0.15 0.11 0.09 0.07
16 8.15 3.62 2.04 0.91 0.51 0.33 0.23 0.17 0.13 0.10 0.08
18 9.17 4.07 2.29 1.02 0.57 0.37 0.25 0.19 0.14 0.11 0.09
20 10.19 4.53 2.55 1.13 0.64 0.41 0.28 0.21 0.16 0.13 0.10
25 12.73 5.66 3.18 1.41 0.80 0.51 0.35 0.26 0.20 0.16 0.13
30 15.28 6.79 3.82 1.70 0.95 0.61 0.42 0.31 0.24 0.19 0.15
40 20.37 9.05 5.09 2.26 1.27 0.81 0.57 0.42 0.32 0.25 0.20
50 25.46 11.32 6.37 2.83 1.59 1.02 0.71 0.52 0.40 0.31 0.25
60 30.56 13.58 7.64 3.40 1.91 1.22 0.85 0.62 0.48 0.38 0.31
70 35.65 15.84 8.91 3.96 2.23 1.43 0.99 0.73 0.56 0.44 0.36
80 40.74 18.11 10.19 4.53 2.55 1.63 1.13 0.83 0.64 0.50 0.41
90 45.84 20.37 11.46 5.09 2.86 1.83 1.27 0.94 0.72 0.57 0.46
100 50.93 22.64 12.73 5.66 3.18 2.04 1.41 1.04 0.80 0.63 0.51
110 56.02 24.90 14.01 6.22 3.50 2.24 1.56 1.14 0.88 0.69 0.56
120 61.12 27.16 15.28 6.79 3.82 2.44 1.70 1.25 0.95 0.75 0.61
130 66.21 29.43 16.55 7.36 4.14 2.65 1.84 1.35 1.03 0.82 0.66
140 71.30 31.69 17.83 7.92 4.46 2.85 1.98 1.46 1.11 0.88 0.71
150 76.39 33.95 19.10 8.49 4.77 3.06 2.12 1.56 1.19 0.94 0.76
160 81.49 36.22 20.37 9.05 5.09 3.26 2.26 1.66 1.27 1.01 0.81
180 91.67 40.74 22.92 10.19 5.73 3.67 2.55 1.87 1.43 1.13 0.92
190 96.77 43.01 24.19 10.75 6.05 3.87 2.69 1.97 1.51 1.19 0.97
200 101.86 45.27 25.46 11.32 6.37 4.07 2.83 2.08 1.59 1.26 1.02
210 106.95 47.53 26.74 11.88 6.68 4.28 2.97 2.18 1.67 1.32 1.07
230 117.14 52.06 29.28 13.02 7.32 4.69 3.25 2.39 1.83 1.45 1.17
240 122.23 54.32 30.56 13.58 7.64 4.89 3.40 2.49 1.91 1.51 1.22
250 127.32 56.59 31.83 14.15 7.96 5.09 3.54 2.60 1.99 1.57 1.27
260 132.42 58.85 33.10 14.71 8.28 5.30 3.68 2.70 2.07 1.63 1.32
270 137.51 61.12 34.38 15.28 8.59 5.50 3.82 2.81 2.15 1.70 1.38
280 142.60 63.38 35.65 15.84 8.91 5.70 3.96 2.91 2.23 1.76 1.43
290 147.70 65.64 36.92 16.41 9.23 5.91 4.10 3.01 2.31 1.82 1.48
300 152.79 67.91 38.20 16.98 9.55 6.11 4.24 3.12 2.39 1.89 1.53
310 157.88 70.17 39.47 17.54 9.87 6.32 4.39 3.22 2.47 1.95 1.58
320 162.97 72.43 40.74 18.11 10.19 6.52 4.53 3.33 2.55 2.01 1.63
330 168.07 74.70 42.02 18.67 10.50 6.72 4.67 3.43 2.63 2.07 1.68
340 173.16 76.96 43.29 19.24 10.82 6.93 4.81 3.53 2.71 2.14 1.73
350 178.25 79.22 44.56 19.81 11.14 7.13 4.95 3.64 2.79 2.20 1.78
360 183.35 81.49 45.84 20.37 11.46 7.33 5.09 3.74 2.86 2.26 1.83
370 188.44 83.75 47.11 20.94 11.78 7.54 5.23 3.85 2.94 2.33 1.88
380 193.53 86.01 48.38 21.50 12.10 7.74 5.38 3.95 3.02 2.39 1.94
390 198.63 88.28 49.66 22.07 12.41 7.95 5.52 4.05 3.10 2.45 1.99
400 203.72 90.54 50.93 22.64 12.73 8.15 5.66 4.16 3.18 2.52 2.04
420 213.90 95.07 53.48 23.77 13.37 8.56 5.94 4.37 3.34 2.64 2.14
430 219.00 97.33 54.75 24.33 13.69 8.76 6.08 4.47 3.42 2.70 2.19
440 224.09 99.60 56.02 24.90 14.01 8.96 6.22 4.57 3.50 2.77 2.24
450 229.18 101.86 57.30 25.46 14.32 9.17 6.37 4.68 3.58 2.83 2.29
460 234.28 104.12 58.57 26.03 14.64 9.37 6.51 4.78 3.66 2.89 2.34
470 239.37 106.39 59.84 26.60 14.96 9.57 6.65 4.89 3.74 2.96 2.39
480 244.46 108.65 61.12 27.16 15.28 9.78 6.79 4.99 3.82 3.02 2.44
490 249.55 110.91 62.39 27.73 15.60 9.98 6.93 5.09 3.90 3.08 2.50
500 254.65 113.18 63.66 28.29 15.92 10.19 7.07 5.20 3.98 3.14 2.55
510 259.74 115.44 64.94 28.86 16.23 10.39 7.22 5.30 4.06 3.21 2.60
520 264.83 117.70 66.21 29.43 16.55 10.59 7.36 5.40 4.14 3.27 2.65
540 275.02 122.23 68.75 30.56 17.19 11.00 7.64 5.61 4.30 3.40 2.75
550 280.11 124.49 70.03 31.12 17.51 11.20 7.78 5.72 4.38 3.46 2.80
560 285.21 126.76 71.30 31.69 17.83 11.41 7.92 5.82 4.46 3.52 2.85
570 290.30 129.02 72.57 32.26 18.14 11.61 8.06 5.92 4.54 3.58 2.90
600 305.58 135.81 76.39 33.95 19.10 12.22 8.49 6.24 4.77 3.77 3.06
640 325.95 144.87 81.49 36.22 20.37 13.04 9.05 6.65 5.09 4.02 3.26
680 346.32 153.92 86.58 38.48 21.65 13.85 9.62 7.07 5.41 4.28 3.46
720 366.69 162.97 91.67 40.74 22.92 14.67 10.19 7.48 5.73 4.53 3.67
760 387.06 172.03 96.77 43.01 24.19 15.48 10.75 7.90 6.05 4.78 3.87
800 407.44 181.08 101.86 45.27 25.46 16.30 11.32 8.32 6.37 5.03 4.07

Scroll horizontally to view all pipe sizes. Values shown in m/s (meters per second).

Summary

Use the Remko Suction Pipe Quick-Select table to size suction piping correctly. Always target the Design 1.2 m/s column for standard applications, and size up for long runs, poor NPSH margins, or viscous fluids. For detailed velocity verification, consult the Complete Velocity Reference Table above. Remember: suction velocity should be ≤ 1.5 m/s (green zone), while discharge can safely run at 2.5-3.0 m/s.

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