On OSI, pouring water in barrels and then removing it was a way to release the barrels and take them home with you. Why doesn't it work here?
Where are you when trying this? Guard zone, non-guard zone, dungeon, owned house, friended, co-owned?
This has never worked that I can recall, though it would be a nice feature. Also, using water pitchers to fill/drain buckets to unlock them was patched out a year or two ago.
One thing to note when looking to update this would be the spawning rare barrels. I would not like to see their rarity lessened through another mechanic. Perhaps spawning the closed top barrels only and having the open barrels be the ones for the water pitcher trick?