Basically, if you do a Google search for "Tefal express leak" [ making sure you get the make right :-) ] , you'll see this is a very cpommon problem with Tefal steam generator irons.
My thought would be to try a few of the descaling suggestions but plan to cut your losses, do some research and buy one with a better reputation.
Acp
August 2017
Automatic Answer
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Try fixfault.com to fix steam irons.