I say, and with Allah's guidance: The leftover water of a snake is disliked to use in purification as a matter of etiquette when there is other water available that is not disliked. It is not disliked when there is no pure water available; due to the necessity of its circulation, as it resides in houses, unlike scorpions, beetles, and crickets; due to their lack of impurity, so there is no dislike in using them. Refer to: Maraqi al-Falah 32, Al-Sayah 1: 465, and Radd al-Muhtar 1: 149, and Allah knows best.