Depends on the type of valve, gate, ball, globe, diaphragm..... as to where
and how the pressure acts. Sounds like the force in tank is greater than the
solenoid actuator force.
For example if a gate valve force is pressure acting over area of gate. Thats
typically a lateral pressure, so solenoid has to overcome the force creating
friction on the gate contact body interface. The gate has an area, x psi acting
over the area, then that gets uptranslated by fact only small perimeter surface
of gate is in contact with body
Regards, Dana.