Water chip

The water purification control chip is the cornerstone of the Vault-Tec Corporation's water purification systems installed in vaults.

Background
The chip that controls the system is a fine example of 21st century electronics. It is a large circuit board with embedded vacuum tubes that regulates the filtration systems inside the water purifier and monitors the output for signs of contamination. While the water chip can be jury-rigged for small scale water purification, it is specifically designed to interface with vault water computers (via a specific slot and jack; the chip still requires independent power supply through its own cord), making it useless for large scale water purification without a vault.

While it is theoretically designed to last, the chips were manufactured by a low-bid contractor, resulting in poor quality and a high failure rate. Such was the case with Vault 13 in 2161, made worse by the fact that the process was too complicated for a workaround system. They also came in boxes with five chips each.

However, the chips are interchangeable and work in any vault water computer, they just require a self-test and reboot after connecting. 

Failing water chip
The events of Fallout begin after Vault 13's only water chip breaks, and the only means to compensate for the diminishing water supplies is to leave and find a new chip. The original Vault Dweller, although not the first to be picked for the task, is sent on a quest to find a replacement in 2161. After encountering many people and places in the wastes of southern California, he finds a suitable replacement chip in Vault 12, the vault underneath the Necropolis, and returns it to Vault 13.

Ironically, due to a mix-up with shipping orders, Vault 8 received the additional water chips that Vault 13 had ordered in place of their second allotted Garden of Eden Creation Kit, which went to Vault 13.

Characteristics
Despite being referred to as a chip, the in-game visuals of the device, both the 3D rendering and the background circuit diagram, indicate that it is built entirely using thermionic valves, not even discrete transistors, in the traditional style of such 50s technology, as a metal box chassis with protruding glass vacuum tubes; the "chip" may not actually contain any silicon at all. The name is also slightly misleading in that the chip itself does not produce or process water, but controls other equipment that does.

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



 * Technically, the water chip is not a chip at all. The term is reserved for devices using integrated circuits, an invention that has never really caught on by 2077, printed on circuit boards. The water "chip" is a large processing unit built on a full metal chassis with thermionic vacuum tubes.
 * The blueprint shown in the background of the intro is actually a schematic diagram for a Moog synthesizer.
 * 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.