Abstract: A pressure regulator apparatus is provided which includes a regulator body having an inlet, an outlet and a passage communicating there between. The pressure regulator apparatus includes a valve disposed within the passage having a valve seat and a valve stem with one end of the valve stem biased toward the valve seat. The pressure regulator apparatus further includes a plunger member connected to the valve stem at an end opposite the valve seat with the plunger member movable axially with respect to the valve seat. The plunger member is further connected to a biasing member so that the plunger member biases the valve stem toward the valve seat to control the pressure of the fluid flowing through the pressure regulator. A flexible diaphragm is connected at an inner end between the valve stem and plunger member and connected at an outer end against the regulator body. The diaphragm is flexible as the plunger member and valve stem move axially with respect to the valve seat.