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Engineering ToolBox > Recommended Suction Flow Velocity of Viscous Fluids
Avoid high velocities in the suction pipes. Higher velocities increases the pressure loss in the pipe and there may be a chance that the pump start to cavitating. As a rule of thumb the suction velocity in front of a pump should be below:
| Pipe bore | Viscous Liquids | ||
| inches | mm | m/s | ft/s |
| 1 | 25 | 0.3 | 1 |
| 2 | 50 | 0.33 | 1.1 |
| 3 | 75 | 0.36 | 1.2 |
| 4 | 100 | 0.4 | 1.3 |
| 6 | 150 | 0.43 | 1.4 |
| 8 | 200 | 0.45 | 1.5 |
| 10 | 250 | 0.5 | 1.7 |
| 12 | 300 | 0.5 | 1.7 |
These values depends a lot of the fluid pumped. More about viscosity and viscosities of different fluids can be read here: