A motor will drive a pump whose job is to create a pressure of water in a reservoir.
The electrical power path is likely to be:
Socket
Fuse
Cable
On/off switch
Pressure switch
Motor
On/off switch (if double pole)
Neutral return (cable etc)
If I were investigating the fault I would begin at the mid point and work from there in the appropriate direction.
Good luck...
Peccavi
April 2010