I say, and with God's success: It is not valid for him to perform tayammum if he is reasonably certain that there is no prohibition from those who have water if he asks for it; because he is asking in a place where water is not scarce, thus it is usually available. See: Al-Ghunya Al-Mustamli p. 69, Al-Radd Al-Mukhtar 1: 167, and God knows best.