Aqua Pura, literally "pure water", is the result of Project Purity finally becoming functional after many years of being defunct. Taken from the Potomac River Tidal Basin, the water has been cleansed of its radioactivity by the now active purifier located inside the Jefferson Memorial.
Drinking the water after choosing to infect it with the modified FEV will result in an additional player debuff effect and, if consumed in large enough quantities will cause death. The reason for this danger is the fact that the Lone Wanderer was actually born outside of a Vault and thus he or she is not immune against the modified FEV, which was designed to kill anyone who had prolonged exposure to the radiation and other mutational effects of the Wasteland.
The debuff effect changes the more water that is consumed. The following shows the effects based on the amount of bottles ingested:
-1 Strength for 12 minutes
-2 Strength for 18 minutes
-2 Strength and -1 Intelligence for 24 minutes
Note: the bottle count stacks with holy water, resulting in death if 4 bottles of any mix of the two items are consumed (i.e. 2 holy water and 2 Aqua Pura).
Note: even if the effects of the debuff have worn off, the bottle count does not reset back to zero; resulting in death on the 4th bottle regardless of how much time has passed between each consumption.
PCPlayStation 3Xbox 360 Giving any amount of Aqua Pura to Water Beggars will result in their death at the next map change, regardless of whether or not the Aqua Pura contains modified FEV.
PCPlayStation 3Xbox 360 Sometimes after drinking Aqua Pura a message will appear saying that "aqua pura has worn off". This is like when a chem wears off but there were no effects to begin with. This message may appear at random times, days after drinking Aqua Pura. This is not really a bug but a scripting quirk. Because tainted Aqua Pura has a debuff effect it's treated like a chem. The taint effect is still applied to the player, but since the effect fails a condition check, the actual debuff and player death chance aren't applied. The pure Aqua Pura is thus also treated as a chem though it has no ill effects; the end result being the "worn off" messages.
Xbox 360 Non-player characters use this as an aid item during firefights. It has the same effects on them if there is modified FEV added to the water. However, non-player characters drinking it will trigger the script that attributes the negative effect to you. In essence, if non-player characters drink many infected Aqua Puras, the script will kill you instead of them.