Unfortunately, there is no specific guidance on how to go about this. Some recommended approaches that may be accepted are as follows:

Figure out if the manufacturer guarantees meter performance up to a certain age or volume of water that has passed through. Then demonstrate that the meters are under that age or water volume.Have the meter or submeter calibrated by a third-party or the project team to verify the accuracy. But remember, if you’re going to perform the calibration in-house, it is recommended that the project team submit a CIR to get approval on the specific approach to calibration.