We're so comfortable with our plumbing system. We turn on the faucet and water flows; we flush the toilet and water flows; we water the garden and water flows from the hose. We take water for granted; however, after the fall of Rome, indoor plumbing disappeared through the middle ages. In Gubbio, in the 14th Century; however, indoor plumbing was available to some. They were able to get water from a source in the mountains and with the sophisticated use of hydraulics, the people from Gubbio managed to have running water on the 4th floor of the buildings housing their elected leaders. There were two fountains also supplied from this water source as well as toilets, but it's not certain how the toilets were cleaned. What is important is that plumbing did exist, albeit through gravity, but certainly not through PVC or copper piping, but through clay/terracotta channels.
Here are a couple of photos of a fountain that was the recipient of the water entering the building.