Drowning in Zaun
So, Piltover is a coastal sea-side city, quite literally sitting between two oceans, with Zaun directly beneath it, the people of Zaun living in the crags and cliffs below Piltover.
People complain about the Gray, but if I lived in Zaun I'd be more worried about the ocean tide or a monsoon, because one bad storm could possibly lead to the entire city flooding.
Which brings me to another point, they very lowest levels of Zaun are called the Sump, a place that's essentially one giant pool of chemicals and trash from above that have created a hazardous waste of an ocean. Has water completely stopped flowing through Zaun, and if so, how?