Impure water purified by scientific treatment

A question on impure water treated by scientific means, in which Ibn Baz distinguished between large and small quantities. ¹

The questioner asked about water impure in origin that had been recycled and filtered until its smell, colour and taste were like natural pure water. ¹

Ibn Baz answered that a large quantity, two qullas or more, becomes purifying again once the change caused by impurity is removed, whether by treatment or otherwise. ¹ He noted that below two qullas the matter is disputed among scholars. ¹ A very small quantity, he said, is not purified merely because the smell, taste or colour of the impurity has gone. ¹ He cited the command to pour out a vessel a dog has drunk from, since the water in vessels is usually little. ¹

The answer is published on binbaz.org.sa, the official site of Ibn Baz's legacy, as fatwa 2476 in the al-Jami al-Kabir series. ¹ The museum records this answer as a historical text attributed to its author; it issues no ruling of its own.