Purity: Hardship (Haraj) And Excessive Difficulty (Mashaqqah)

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 662:

If procuring water or using it causes someone hardship or excessive difficulty that cannot normally be endured, he can perform tayammum. However, if he endures it and performs wudu or ghusl, his wudu or ghusl is valid.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)