system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why do we use clean, potable water in toilets?
gpt
A separate water supply system for toilets would cost too much to build and maintain in a city. The water in it can't so dirty to cause gunk to deposit in storage tanks, pipes and the toilet, or be toxic for plant life that it can't be used for watering a garden.