The World Federation One Stop Fiqh

Ruling 664

If apart from having pure water for wuḍūʾ or ghusl a person also has impure water that is sufficient only for drinking, he must keep the pure water for drinking and perform prayers with tayammum. However, in the event that one wants the pure water for those who are dependent on him, he can perform wuḍūʾ or ghusl with the pure water even if his dependants are compelled to quench their thirst with the impure water. In fact, if they are unaware of the water being impure, or they do not refrain from drinking impure water, it is necessary for him to use the pure water for wuḍūʾ or ghusl. Similarly, if one wants water for his animal or for a child who is not bāligh, he must give them the impure water and perform wuḍūʾ or ghusl with the pure water.