Taking your water sample:
Use a plastic bottle of between 250mL and 1000mL. Old water bottles are fine for this but
avoid using any bottle that has previously had carbonated liquid in it.
To take your water sample open the tap and allow it to flow a few minutes to remove standing water from your pipes and then without interrupting the flow rinse the sample bottle several times before finally filling to overflowing. Turn off tap. Cap tightly and tape the cap to prevent it undoing itself whilst it is in transit. The water that is run to waste may be run into a bucket and used for something else.
Label the bottle with the date as a minimum and preferably the source plus your name.