Pump water suction flow velocity

What is the recommended velocity for water flow at inlet of a pump ?

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Section summary
1. Flow velocity at the inlet of a pump
2. Water flow velocity design recommendations
3. Water velocity in pipes calculation

1. Flow velocity at the inlet of a pump

This page is giving references to design the inlet piping of water pump to make sure the velocity of water is high enough.

When designing or troubleshooting an existing water pumping system it is important to check what will be the velocity of water in the pipe at the inlet of the pump is not too low. Indeed, if the flow is too low, then the pump risks to be starved in water which may lead to cavitation and lower capacities than foreseen.

2. Water flow velocity design recommendations

The following velocities in the suction pipes of a water pump are recommended, depending on the pipe diameter :

Pipe Diameter Water suction flow velocity recommended
Inches mm m/s ft/s
1 25 0.46 1.5
2 50 0.49 1.6
3 75 0.52 1.7
4 100 0.55 1.8
6 150 0.6 2
8 200 0.75 2.5
10 250 0.9 3
12 300 1.4 4.5

3. Water velocity in pipes calculation

The velocity of water in pipe can be calculated with the following formula :


With :

u = water flow velocity (m/s)
Qv = water volumetric flowrate in pipe (m3/s)
D = pipe diameter (m)


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