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Suction Pressure Gauge – 4.12.2

Gauges are used to measure pressure on both sides of the fire pump when in operation and during the regularly scheduled nonflow testing required by NFPA 25. The gauges should be of sufficient quality to provide a reasonably accurate pressure reading, since they are used for testing purposes on a weekly and sometimes annual basis. These gauges should be calibrated each year to maintenance accuracy.

When there is a possibility of a suction pressure below 20 psi (1.3 bar), the suction pressure gauge is required to be a compound gauge capable of registering negative pressures. This gauge provides the pump operator the ability to monitor the suction pressure to ensure that operating pressures comply with 4.16.3.1.

If a fire pump starts to draw a negative suction pressure, there is a possibility that both the fire pump and the suction piping could cavitate

4.12.2 Suction.

4.12.2.1 Unless the requirements of 4.12.2.4 are met, a gauge having a dial not less than 3.5 in. (89 mm) in diameter shall be connected to the suction pipe near the pump with a nominal 0.25 in. (6 mm) gauge valve.

4.12.2.1.1 Where the minimum pump suction pressure is below 20 psi (1.3 bar) under any flow condition, the suction gauge shall be a compound pressure and vacuum gauge.

4.12.2.2 The face of the dial shall read in inches of mercury (millimeters of mercury) or psi (bar) for the suction range.

4.12.2.3 The gauge shall have a pressure range two times the rated maximum suction pressure of the pump.