SURGE / RELIEF
Protects system from overpressure by exhausting excess pressure. The valve may only have to operate intermittently to prevent pressure surges that might occur on pump start, pump stop, or sudden downstream valve closure.

 

BYPASS PRESSURE CONTROL
Valve keeps pumping system at a constant pressure by bypassing back to source. Provides accurate pressure control when system demand varies widely

 

BACK PRESSURE / SUSTAINING
Valve allows flow when inlet pressure is above the set-point thus preventing inlet pressure from falling too low. Prevents demand from “robbing” the source, or keeps pump “on its curve.”