Opening the faucet in your home should not be taken for granted. If not for pressure, the water would not move at all. Pressure is created by a difference of altitudes, or height. Water pressure for home or factory use is created by a water tower, or a pump and pressure tank.
Almost every town and city has a water tower, usually high on a hill. It's a large reservoir or tank that holds the water supply. The water is taken from the ground, lake or a river, purified and through the use of large water pumps, then piped into these water towers or tanks. The height of the tank determines the amount of pressure that the water supply will have. The general rule of thumb is that for every 2.3 feet of height, a pressure of 1 lb. will be created in a 1-inch diameter pipe. Water pressure is described in pounds per square inch, or PSI. As an example, if a water tower is 240 feet tall, the water pressure at the base of that tower would be approximately 100 PSI. Of course, this type of water pressure would burst every pipe in your home, so a water pressure regulator must be installed at every water meter.
A water pressure regulator adjusts the amount of pressure entering into your home by a large spring and rubber diaphragm. These two components will only allow so much pressure into your homes piping system. The pressure regulator will generally sit before the water meter as most meters can only handle low pressures and will be damaged by the higher pressure provided by a towns water supply.
A water pump with a pressure tank is used to bring up well water. The water pump will pull or push water from the well. The pressure tank holds a certain amount of water to be used. Inside that water tank is a rubber bladder that is filled with air to help keep the water system at a certain working pressure so the water can flow. A pressure switch opens and closes a set of electrical contacts that controls the electricity to operate the pump. In this instance, height is not used for the creation of water pressure; instead, a closed system of the water piping and the rubber air bladder is used. The air bladder is generally kept at a certain air pressure, like the tires on your car or truck.