A water chip is a device which regulates the filtering and recycling systems of a water purifier and monitors the output for any contamination. It is a standard piece of equipment included in all Vault-Tec Vaults.
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. On the second level of Vault 8, hundreds of them can be found and taken, though they aren't very valuable for monetary bartering.
The game's referral to the device as a "chip" is questionable given that, in the Fallout universe, integrated circuits (the origin of the word, as in "silicon chip") were apparently never invented. All technology relies on masses of discrete components and consequently are huge and cumbersome.
Indeed, 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 50's 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.
Behind the scenes
- The blueprint shown in the photo is actually a schematic diagram for a type of vacuum tube radio receiver.
- Through an ironic twist of fate - primarily due to the Guardian of Forever - the Chosen One in Fallout 2 can be shown as the guilty party in breaking Vault 13's original water chip by traveling back in time to the Fallout era, setting that story in motion (whether or not this is canon is debatable).