How can I fix my tefal express generator iron?

As the orange light was flashing I flushed out the water tank as per instructions
Once I started to iron again water is dripping out of the screw cap at the bottom
The screw is properly tight.
It just seems that a washer is missing but having checked other models this is not the case
You can also see the steam escape from the cap

audrey adams
February 2009