The events of Fallout begin after Vault 13's 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, but not the first to leave the vault, is sent on the quest to find a new one 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.
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.