The answer to 'how does pressure regulator work' is a pressure regulator is a device that controls and maintains the water pressure in a plumbing system at a consistent, safe level. It does this by automatically adjusting the water flow to prevent excessive pressure from damaging pipes, fixtures, and appliances.
The pressure regulator is typically installed near the main water supply line, often right where the water enters the home. It contains a spring-loaded valve that opens and closes to adjust the water pressure. When the pressure is too high, the valve opens to release some of the water flow. When the pressure is too low, the valve closes to maintain the desired pressure level, usually between 40-80 PSI.