system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: In cities where the tap water is clean enough to drink, how does the water stay clean throughout the whole process to get to the your faucet?
gpt
The pipes are clean. The pressure in them keeps things out of the pipes as well.  You’ll see water companies issue “boil water” notifications if they lose pressure or have a break in the line that could let nasty stuff in.   After that, they’ll flush the lines and usually add some chlorine to the water to kill nasty germs.