City water system question – How long will water flow?

My local city lists that it has 35 million gallons of water storage capacity. It says the average daily use in the city is 13 million gallons per day in the summer and 7.5 in the winter. Does that mean that there is 3-4 days of water that will flow through the household faucets by gravity if the pumps that fill the towers are offline? We are talking about a typical suburban city with big tall water towers and short buildings. In my simplistic view of the physics, as long as there is water in…