Most urban water supplies use reservoirs of water high up so that gravity does the work of keeping the water moving. At that point, all you need is big enough pipes that the flow rate doesn't slow the water down enough to cause problems. Too much flow in too small a pipe increases the speed and thus the resistance to flow reducing the pressure at the other end (pressure is only constant at the same level when the water isn't moving). These supply pipes can be over a meter in diameter, sometimes even larger. The size steps up, the more properties are supplied be the pips - where I am its generally 15-25mm for a single house, 100mm along most streets, 300mm feeding multiple streets etc. A recent project in my city was a 3m diameter pipe from the reservoir in the hills outside the city

Depending on the terrain around the city, the main storage areas might be too low for this to work properly, in which case, you can use pumps or water towers resupplied with pumps. Particularly tall buildings may need to use pumps or their own tanks in the top of the building to ensure the pressure is maintained as they may be higher than the main reservoirs or close enough to reduce the pressure below the required level.