I checked a French dictionary, and "tuyau" is the word for a water pipe, but "pipe" is the word for a smoking pipe.
The title refers to Magritte's pipe pictures, which are of a smoking pipe -- so I guess the level designers were making a joke that works in English because we have the same word for both, but they didn't realise it doesn't work in French.
(Or maybe it's a deliberate double joke -- because a water pipe really is not "une pipe"!)