The World Federation One Stop Fiqh

Ruling 152

With regard to a tanūr20 that has become impure with urine, if water is poured once into it from above in a manner that it reaches all its sides, it becomes pure; and the recommended precaution is that this should be done twice. However, in case it has become impure by something other than urine, then after removing the impurity, it is sufficient to pour water once into it as described. Furthermore, it is better to make an indentation at the bottom of it so that water collects there; then, the water should be emptied out and the indentation should be filled in with pure soil.

20 A tanūr is a fire-heated oven for baking bread.