The Water pitcher was a jug that contained a type of water that was poisonous upon consumption. Although it has the option of drinking it, consumption gives instant death. it is presumed that this was the water was affected by the radioactive mineral ore as descibed in Engineer Hutchinsen's notebook. It can be poured onto the the Rifle-man near the elevator entrance, which turns it to stone n to open the door, and results. This is covered upon in the Poem by a convict.