The fountain your looking for is in Starcrest commune. Once you obtain the bucket of water you must walk in order to prevent it from spilling(you can do this by pressing k and selectin the walk/run icon). The fastest way to get back to Eldar grove from Starcrest is South Qeynos to North Qeynos and bak to Eldar. Couple words of advice when in Starcrest zone as far away from the gate as possible there seems to be glitch right by the gate that makes ya spill the water, the other you must select walk mode after every zone. Good luck.
Wudang Gungfu 21 monk(Innothule)