The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, narrated to me from Abu al-Qasim Ja'far ibn Muhammad, from his father, from Sa'd ibn Abdullah, from Ahmad ibn Muhammad, from Muhammad ibn Isma'il ibn Bazi': I wrote to a man asking him to question Abu al-Hasan al-Ridha عليه السلام about the matter. Imam عليه السلام said: "The water of a well is abundant and is not corrupted by anything unless its smell or taste changes. In such a case, water should be drawn from it until the smell disappears and its taste becomes pure, because it has a continuous source."