The answer to 'how does pressure regulator work' is a pressure regulator is a device that controls the water pressure in a plumbing system. It is installed on the main water supply line to a home and reduces the incoming water pressure to a safe and consistent level for the home's plumbing fixtures and appliances.
The regulator contains a spring-loaded diaphragm that responds to changes in water pressure. When the incoming pressure is too high, the diaphragm closes partially to restrict the flow and lower the pressure. When the pressure drops, the diaphragm opens back up to allow more flow. This automatic adjustment maintains the desired pressure, typically between 40-60 PSI, which is the optimal range for most residential plumbing systems.