Water chip

The Water Chip, also called the water purification control computer system chip,' is a piece of technology in Vault-Tec Corporation vaults. The events of Fallout begin after Vault 13's only water chip breaks, and the Vault Dweller is sent out to find a replacement.

Background
The chip is an electronic device that regulates the filtering system of a water purifier and monitors the output for any contamination. They are prone to failure, and unless used in a vault with the proper equipment, they are useless.

Due to a shipping error, Vault 8 received a box of surplus water chips intended for Vault 13, and Vault 13 received Vault 8's second GECK. The chips were packaged in groups of five to a box. 

Locations

 * Vault 12's command center, in a computer.
 * One can be found in a locked footlocker in Vault 13.
 * A grand total of 420 chips can be found on the second floor of Vault 8, in crates in certain rooms that can only be opened with a high Lockpick or Strength.

Behind the scenes

 * The blueprint shown in the background of the intro is a schematic diagram for a Theremin. It is sourced from an issue of Radio and Television News from January 1964, found on p.38 in an article about the Theremin by Robert Moog.
 * In Fallout 2, the Guardian of Forever special encounter allows the player character to break the water chip and set the events of Fallout in motion.