People tend to take the water supply for granted. You turn on a faucet, and clean, drinkable water comes out. You find no reason to be concerned. Of course, if the water made you sick or had a strange look, smell or taste, then you might want some answers.
The reason that we have this good supply of clean water is because the City of Toronto goes to great lengths to ensure that the water is clean and safe. In guaranteeing this supply of clean water, the city has to protect the water supply from contaminants. In its efforts to protect the water supply, the local government has to ensure that the water supply is protected from backflow.