|>>|| No. 420502
>Water is basically sterile, which is why it is safe to drink out the tap.
No, it's not. It needs to be within certain limits as to its pathogen content, but it's not going to be sterile in a biological sense. In order for tap water to actually be sterile, you would have to run it through a sterile filter system, and the pipes would then have to be hermetically sealed to keep pathogens out, and would still have to be sanitised regularly.
What makes the water in your pipes relatively safe to drink, next to your local water supplier's adherence to sanitary standards, is that water pipes inside buildings are usually made of copper (although in some cases plastic or polymer). Copper tends to let off copper ions into water, and these copper ions are toxic to single cell organisms and pathogens. While they are not toxic to humans, and we actually need traces of copper in our diet.
The biocidic effects of copper against pathogens are so strong that there are trials going on in hospitals where copper alloys are used for surfaces that attract germs, such as sinks and door handles.