The danger in unused water may be avoided by putting in it a piece of iron or an iron vessel (Bet Yosef on the Tur, and Isserles' note to Shulḥan Aruk, Oraḥ Ḥayyim, 455, 1; Be'er Hetev, to Yore De'a, 116, 5).
He also left in manuscript Akeret ha-Bayit (The Barren One of the House; compare Psalms cxiii. 9), a commentary on another division of the Shulḥan Aruk; namely, Ḥoshen Mishpaṭ.