Which instrument indicates flow in gallons per minute?

• A. Flow meter
• B. Compound gauge
• C. Bourdon tube
• D. Vacuum gauge

Answer: (A)

Measuring flow rate is the key idea here—how much water is moving per minute, expressed as gallons per minute. The instrument that directly provides this readout is the flow meter. It sits in the discharge line and detects the rate of water flow, often using mechanisms like a turbine or differential pressure to convert movement into a GPM value. This is exactly what you need to know for pump operations, nozzle selection, and ensuring your attack line has the desired capacity.

The other instruments measure pressure or vacuum, not flow. A compound gauge shows both positive pressure and vacuum; a Bourdon tube gauge is a pressure gauge; a vacuum gauge reads negative pressure. None of these give a direct GPM reading, so they don’t indicate flow rate.