how do pressure regulators work
A pressure regulator is a control valve that reduces the input pressure of a fluid to a desired value at its output. Regulators are used for gases and liquids, and can be an integral device with an output pressure setting, a restrictor and a sensor all in the one body, or consist of a separate pressure sensor, controller and flow valve.
An adjustable spring loaded diaphragm inside a water pressure regulator reduces the pressure of the water in the line within the valve body. Water coming into the valve is constricted and then released at a reduced pressure.