Estimating GPM from a New 6-Inch Irrigation Well

Trust the Driller's Flow Test

A new 6-inch well, 140 ft deep with 80 ft of perforations and static water at 11 ft, is rated at 120± GPM by the driller. The owner questions this figure and wants to verify with a centrifugal pump at ground level for flood irrigation (minimal head).

Why the Paperwork Is Reliable

Drillers typically perform a flow test (pump test) to determine yield. Replicating that test requires a pump, piping, and measuring equipment—a significant investment. The driller's number is the best available estimate.

Critical: Pump Setting Depth

When the pump runs, it draws the water level down (drawdown). The pump intake must be set below the lowest expected drawdown level, but not so deep that it sits in the screen zone where flow is restricted. The optimal depth balances flow and submergence—usually midway between static level and maximum drawdown.

Consult the driller for the recommended pump setting depth based on their test data.