A breast pump system comprising a solenoid valve is disclosed. The breast pump system further comprises a power source which is arranged to supply electrical power to the solenoid valve so as enable the solenoid valve to move between first and second positions. The breast pump system also comprises a controller configured to detect a change in inductance of the solenoid valve which is indicative of the solenoid valve moving from first to second position and a control action in which the vacuum pump is stopped.
