A Pond will not Qualify as a Large Pond According to the Shari'ah when It is not Ten by Ten even though it may be very Deep

Q: Taharaat-58: The pond in our Masjid measures 4.6x8x13.9 feet, giving It a capacity for more than 14000 litres of water. I do not think that even a large well has so much water. Will this pond be regarded as a large pond in terms of the Shari'ah (a pond that will not be rendered impure by any impurity unless the taste, colour or smell changes)? What will happen if any impurity falls in? Does the specification of ten by ten mentioned in the books of Fiqh refer to dimensions or the capacity? Therefore, if the length and width of the pond fall short of ten by ten as in our case, will the extra depth not compensate for the short fall since the volume is still large? Will this pond then be regarded as a large pond in term of the Shari'ah?

Answer: The pond in question is not a large pond in terms of the Shari'ah because the depth will not compensate for the shortfall in length and width. Although wudhu will be permissible from this pond, a small amount of impurity will render the pond impure. Therefore, if it is possible, the size of the pond should be increased and if this is not possible, perhaps a tank can be built above it. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2