Various methods to prevent vortex formation

Normal water level in the basin must be at least 6 inches above the top of the pump casing. 

Water velocity in the pump suction line should not exceed 8.5 ft/sec. In the discharge line, the water velocity should not be greater than 12 ft/sec to avoid excessive erosion of piping (especially where water containing grit is used). 

Each pump should be isolated with suction and discharge valves. 

Pumps should be provided with strainers at their suction inlet, normally with 3/8-inch screen openings to avoid leaves, pieces of wood and other foreign material from getting into the pump impeller. 

The design capacity of the pumps should be 110-115% of normal capacity. Pumps should have suitable spares, depending on the number of pumps provided for example, two 100% capacity or three 50% capacity pumps. For a large installation, where more than two pumps are required to operate simultaneously, one spare machine every two pumps should be provided. 

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Figure 7.2 Various methods to prevent vortex formation.

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