Fourth:

682. If a person fears that if he uses water for Ghusl or Wudhu, he himself or his wife or children or his friends or someone who is under his guardianship such as his servant or maid will suffer an acute thirst, which may result in illness or death, or it may cause intolerable hardship, he should perform Tayammum instead of Wudhu and Ghusl. Similarly, if he fears that an animal which he owns, may die of thirst, he should give it a water and perform Tayammum instead. Similarly, if he does not give water to his dependents whose protection is his responsibility, may die due to thirst.

683. If besides the Pak water which a person has for Wudhu or Ghusl he also has Najis water enough for drinking for himself and his dependents, he should keep the Pak water for drinking and pray with Tayammum. However, if water is required for an animal, it should be given Najis water to drink and Pak water be used for Wudhu or Ghusl.