Impurities in a Large Body of Water

Q: If only part of a large body of water changes because of impurity, does the whole thing become impure?

A: Not always. A large body water (like a pool or tank) is considered pure and purifying as long as it’s at least the size of two qullahs (roughly 58 US Gallons) and has not changed in smell, color, or taste.

But if part of that water changes because impurity fell into it, here’s what happens:

• The part that changed is impure.

• The rest of the water is still pure—as long as it hasn’t changed and it’s still two qullahs or more.

However, if the remaining unchanged water is less than two qullahs, then the whole thing becomes impure—even if some of it didn’t change. That’s because the pure part is now touching the impure part, and it’s not enough water to override that contact with impurity.

So the key is:

• If the changed part is small and the rest is still a lot (two qullahs or more), you can still use the rest.

• But if the clean part is too little, then you can’t use any of it.

Source: Kashshāf al-Qināʿ