It is narrated from Sayyiduna Wathilah bin al-Asqa' (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "None of you should say, 'I have poured out water,' but rather let him say, 'I am urinating.'"
Hadith Referenceالمعجم الكبير للطبراني / باب الواو / 18370