Water chip

The Water Chip is a device which controls the water recycling and purification process in all Vaults. The original Fallout game began when Vault 13's water chip apparently broke and there were no replacements. The original Vault Dweller is sent to find a new one, and finds one in Vault 12, the vault underneath Necropolis and returns it to Vault 13. Due to a mix up in shipping, Vault 8 attained Vault 13's additional Water chips, in exchange for their additional Garden of Eden Creation Kit.

Through another strange twist in fate, primarily due to the Guardian of Forever, the Chosen One in Fallout 2 actually broke the original Vault 13 water chip by traveling back in time to the Fallout era, setting that story in motion. (Whether or not this is canon is debatable.)

Apparently, many vaults are in short supply of water chips, or run low on them over time. In Fallout 3, the Lone Wanderer can opt to force the residents of Vault 101 to leave their sealed vault by destroying what is apparently their only remaining water chip.

hydroprocesor Водный чип