Purity: Wudu from a Pool with Usurped Bricks
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 273:
If a brick or stone of a pool, for example, is usurped, in the event that drawing water from the pool is not commonly regarded as using the brick or stone, there is no problem. However, in the event that it is regarded as using the brick or stone, then drawing water from the pool is unlawful but the wuḍūʾ is valid.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)