Fix the Necropolis water pump

Fix the Necropolis water pump is a side quest in Fallout.

Walkthrough
After talking to the underground ghouls of Necropolis, travel to the watershed area and then enter the sewers. Go to the back of this section of the sewers and you should find a pile of junk. Alternatively, you could already have grabbed the junk from a crate in Jacob's Weapon shop in The Hub Old Town. These will also fix the water pump.

Get past the super mutant guards back in the Watershed area, by convincing Harry that you are a robot (speech), telling him you're leaving when he says non-ghouls are not allowed, or by simply killing the super mutants. However it is advisable to retrieve the water chip prior to killing the mutants, as each mutant alive during extraction of the chip will add a bonus 250 XP (since there's 6 super mutants in total, this means an additional 1500 XP). Go to the water pump and use your repair skill to fix the pump. If your repair skill is too low, you can travel back to speak to the leader of the underground ghouls who will give you 3 copies of Dean's Electronics. It may take a few tries for a low repair character, but once the pump is successfully fixed you will receive 1000 experience. Now you can rest easily knowing that jacking the water chip won't cause the poor hapless ghouls to die of thirst. Please note that it is quite possible to break these parts (and injure yourself in the process) if your Repair skill is truly abysmal. The truly unintelligent may require Mentats in order to complete this quest.

Set wants it fixed
An alternative way to get this quest is from Set. If you have already searched Vault 15 and are in possession of the "junk", Set will have his surly minion, Garret, fast travel you to the water pump. Garret will watch you attempt to repair the pump at gun point.

Reward
1000 XP for repairing the pump, 1000-2500 XP for retrieving the water chip from the Vault depending on number of mutants left alive.