What is a Pressure regulator valve?

A regulator is simply a valve with a preset pressure point that causes the valve to open and close. A pressure sensor (a diaphragm with an adjustable spring) is on the side of the valve that the pressure you want is on. When the desired pressure (we will use 50psi) is reached, it causes the diaphragm to expand against the spring.The diaphran is connected to the valve and when it expands, it closes the valve, letting no more pressure to build. when you flush a toilet or turn on the sink, the diaphragm contracts opening the valve wider and wider until enough water is flowing in to raise the pressure expanding the diaphragm to close the valve.

the diaphragm is just like a ballon, the more pressure, the more it expands.

the set screw on most regulators puts more or less pressure on the diaprham raising or lowering the amount of pressure needed to move the diaphragm enough to close the valve.

do not confuse the regulator with the pressure switch on a pump system. they are not the same. the job of the regulator is to keep constant pressure in your system. the pressure switch on pumps works about the same but has two preset pressures. the first to turn a pump off when the desired pressure is reached and the second to turn it back on. the off pressure is always higher then the on pressure by about 10psi or your pump would be constantly turning on and off.