Wa`alaikum Assalam Warahmatullahi wa Barakatuh

In his very beneficial book (Al-Makayeel Wal Mawazeen Ash-Shar’iyah) Islamic Measurements, our teacher Shaykh `Ali Gomaa Ash-Shafi`ie, the Grand Mufti of Egypt (May Allah preserve him and benefit us with his knowledge in both worlds) mentions:

القربة ظرف من الجلد يخرز من جانب واحد, وتستعمل لحفظ الماء واللبن ونحوهما.

مقدار القربة: مائة رطل بغدادي

فهي عند الحنفية: 40.625 كيلو جرام

وعند الجمهور: 38.250 كيلو جرام

Qirbah: Is a container made of leather which is stitched from one side. It is used for the preservation of water, milk and similar things.

The measurement of Qirbah is: 100 Ratl (rotl)

In the hanafi madhhab it is equal to: 40.625 Kg

According to the majority (the rest) it is equal to: 38.250 KG

It is worth noting that five qirab is equal to Qullatayn (2 Qullahs) as well. In the Shafi`ie madhhab, when water reaches the level of two qullahs, it is not contaminated by najasah (impurity) anymore.

One qullah is around: 95 kg according to the majority of schools. Therefore, we can say, that if we have 190 kg of water, that will be an amount that is not affected by najis.