In order to ensure the maximum precision of your data, it is recommended that the queuing time is measured by observations instead of interviews with the target groups. The following procedure is proposed:
1) Randomly select water points across different locations of your operation. Specify for each water point the time period of your monitoring (for example, 1 day, from 7am until 7pm). Assign a sufficient number of data collectors (for example, one person monitors in the morning, the second in the afternoon).
2) Prepare a simple recording sheet where the data collector records the water user's identification, arrival time and the time when s/he started collecting water.
3) Collect the data by randomly selecting newly arrived users (do not observe all users - select just those which are easy to recognize from other users - for example, based on their distinct clothes).
4) Calculate the indicator's value by summing up the individual waiting times of the observed water source users and dividing it by the total number of observed users.