If the water supply is cut off before I complete my ablution (wudu'), how do I complete it with tayammum?

If water is cut off during ablution, and he finds other water, he should complete his ablution with it if the interruption is short. Otherwise, he should repeat the ablution as a precautionary measure. However, if he does not find other water, he should perform tayammum (definition) for the remaining parts of the ablution. This is the view of the Hanbalis and is the more cautious approach. Tayammum is performed with one strike on pure earth to wipe the face and hands.