Let's assume that you get your water from the local water department through pipes buried below the streets. In other words, you don't have your own well in your back yard. Chances are that you get your water through the magic of gravity or pumps. Cities and towns build those big water towers on top of the highest hills and then fill them with water. So even if you live on a hill, there's a good chance the water tower is higher than your house. Water goes down a large pipe from the tower and through an intricate network of pipes that eventually reaches your house. One way to assure that you have enough water pressure at your house is to make the pipes smaller and smaller as they get further away from the water tower. But, still, water pressure diminishes as it travels along those miles of pipes. That is why the house at the end of a big subdivision might have less water pressure than the house at the front.