Aqua Pura

Overview

Aqua Pura is only available if the Broken Steel DLC has been installed and the player has beaten the game. Aqua Pura either restores 20 health or temporarily subtracts 2 Strength and 1 Intelligence depending on what actions were taken by the Lone Wanderer at the end of Fallout 3. If the player achieved James's vision of a better Wasteland by activating the purifier or having anyone else activate the purifier then some water in the Capital Wasteland will not have radiation and will give more health for drinking it. This is most prominent around the Jefferson Memorial. However if the player followed what John Henry Eden told them to do by inserting the modified FEV vial and activating the generator then a lot of the water, especially in D.C. becomes even worse than it already was. After the events of Fallout 3 both Tainted Aqua Pura and Aqua Pura will be found in bottles around the Wastes. Aqua Pura is essentially exactly like regular Purified Water except it is valued for less caps. Tainted Aqua Pura is extremely harmful to anyone who drinks it, giving Tainted Aqua Pura (or regular Aqua Pura because of a bug) to Water Beggars will kill them. If the Lone Wanderer drinks too many Aqua Puras (usually more than two) they will die.
Aqua Pura weighs 1 pound and is valued at 6 caps. 

Quests

There are several quests associated with Aqua Pura:

Holy Water: This quest is picked up by asking Scribe Bigsley what you can do to help. During this quest a radiation worshiping cult operating out of Springvale is stealing Aqua Pura and giving people heavily (sometimes fatally) irradiated water.

The Amazing Aqua Pura!: A charismatic ghoul in Underworld named Griffon is passing off regular Dirty Water as Aqua Pura (which he calls Aqua Cura), claiming it confers side effects that it doesn't give. 

Protecting the Water Way: This quest revolves around Aqua Pura caravans that have gone missing. The Lone Wanderer has to find out what is attacking the caravans.

Bugs

When continuing the story with Broken Steel many enemies will use Aqua Pura as a health item, sometimes using it in combat. However the effects it has on them are the same as tainted Aqua Pura, regardless of the status of water after the ending. If they drink too much of the water the game will activate the script that kills the player after drinking too much tainted Aqua Pura. This will result in the player dying in a fight after an enemy drinks more than two Aqua Puras.