For an initial meter reading to be valid, which of the following must NOT occur?

For an initial meter reading to be valid, it is essential that the meter operates under proper conditions. If the meter is leaking, it compromises the integrity of the measurement, leading to inaccurate readings. A leak can result in loss of fluid, which may affect flow measurement and result in erroneous data being recorded.

In contrast, when considering the other conditions mentioned, having a stable liquid level ensures that there are no fluctuations that could influence the reading. Similarly, a stable temperature is critical for maintaining consistent properties of the liquid being measured, which can affect density and flow characteristics. Finally, foam on the liquid surface can interfere with the measurement process by altering the effective surface area or causing fluctuations in readings. Therefore, for an accurate initial reading, the presence of a leak must be avoided, making it the condition that must NOT occur.