How big of a well tank do I need?

The minimum rule of running time is any pump that works at 10 gallons/minute (GPM) or lower should produce a gallon/minute of running time. (For example, flow of 10 GPM x burning capacity of 10 gallons.) More than 10 GPM should produce 1.5 gallons/minute of running time.Any pump that operates at 10 gallons per minute or less should be producing one gallon per minute. 10 gallons of flow rate x 1 is 10 gallons of drawdown capacity. 1.5 gallons per minute is what it should be for anything over 10 GPM.