IPF Rev0204
11
FLOW RATE MEASURING INFORMATION
•
The location of the flow sensor in the plumbing system is critical. The flow at
and around the sensor must be laminar, or smooth, to ensure accurate flow rate
measurement. There must be enough straight pipe run before the flow sensor location
to allow the stream to stabilize into a uniform flow.
•
Plumbing systems are always unique and may cause small deviations in the
factory flowmeter calibrations. It is recommended to check flowmeter calibration after
installation.
•
Flowmeters should be checked from time to time for accuracy and recalibrated
as necessary. Calibrate at the most frequently used flow rate or use the guidelines
provided by NFPA 1901. (Refer to Table 2.)
•
Plumbing components upstream of a flow sensor that tend to increase stream
turbulence may cause erroneous flow rate readings. Typical components would include
a valve, flange or elbow, sudden or multiple bends in the piping, or an increase in pipe
diameter. In these cases it may be require that a short length of hose (perhaps a 10 foot
section) be installed upstream of the portable flow tester flow tube to stabilize the
flow. (The hose diameter must be the same as the flow tube diameter.)
Table 2. Flowmeter Calibration Flow for Each Pipe Size
Note:
(Reference NFPA 1901) Each fowmeter shall be calibrated to an accuracy of ±5
percent when flowing the amount of water shown in for the pipe size in which it is
mounted.
Pipe Size
Flow
Inch
mm
GPM
LPM
1.5
38
90
340
2
52
160
600
2.5
65
250
950
3
75
375
1400
4
100
625
2400
