Siemens has picked Goldman Sachs to advise on the sale of its Water Technologies unit, part of the engineering conglomerate's efforts to streamline operations and stay competitive in a weak global economy, two people familiar with the matter said. Siemens, Germany's second-most valuable company which makes products ranging from fast trains and gas turbines to hearing aids, in November announced it plans to sell the water unit with annual sales of about 1 billion euros ($1.35 billion).