The Case of a Well and Things that May Fall in It (Fatwa best explains Ahadith 2-12 as well as the following chapter.)

11. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from al-Husayn ibn Sa‘id from al-Qasim ibn Muhammad from Ali ibn abu Hamzah who has said the following: “I once asked abu ‘Abd Allah, Alayhi al-Salam, about the falling of feces into a well. He (the Imam) said, ‘Ten buckets of water must be taken out and if it has disintegrated then forty or fifty buckets of water must be taken out.’”