Fire pump flowmeters may be used to determine the discharge of a fire pump. Water from the pump is temporarily directed through the flowmeter, then to atmospheric drain or back to the water supply source. It is important that the flowmeter not be connected directly back to the pump suction. This arrangement does not adequately test the condition of the water supply. These flowmeters are calibrated to measure the fire pump output directly in gal/min (dm3 /min). A control valve is provided in the flowmeter line. This valve must be completely closed, except when the flowmeter is in use. Unless otherwise noted in the listing, these systems have 175 psi (1205 kPa) rated working pressure.