Elven Water: Use it?

[trentjaspar]

Hi all...recently got the Elven Water for the Cold Brook quest. It can refill your mana to full 3 times. It appears that there's no bad consequence for this and you keep the vial (even if empty) so it seems like it can still complete the quest normally...but...I don't want to screw up a quest because I'm drinking all of their water!

Any downside to swigging the thing dry before turning it in for the quest? It doesn't lessen the reward or anything, does it?