The valves in series 1132 are pilot operated diaphragm solenoid valves. Their operation depends not only on the magnetic field produced by the current flow into the coil, but also on a minimum inlet pressure, which is necessary to:

• Open the diaphragm and keep it lifted off the main opening
• Close the diaphragm and ensure the tightness on the main opening

Opening / closing of main valve seat is controlled by the diaphragm while opening/closing of pilot seat is controlled by the mobile plunger of the coil.
These valves cannot work with zero differential pressure.