What is the ruling regarding the impurity of a large body of water, such as pools or reservoirs (Masani') on the Mecca road, which cannot be drained?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
Water in large pools, like the Masani' built for pilgrims which hold a large volume, is not rendered impure by anything unless its color, taste, or smell changes. No scholar is known to dissent from this ruling.
Supporting text
Scholars agree that large water bodies, like the sea, if fouled by impurity that does not change its color, taste, or smell, remain pure and one may perform ablution from them. The consensus is that if the water is great enough that it cannot be drained, it is not impure except by human urine or flowing excrement, concerning which there are two narrations from Ahmad, the more famous stating it becomes impure by such contamination.