I have never used a bucket brigade, I use a level operated system to flood the room at will with very little work once set up. It might be worth a try.
I have a 7x7 room used for growing and next to it a 2x7 room used to store water for when I want to flood. They are connected by a hallway that has a door in it. The door is attacked to a lever so I can let water in whenever I want. The reservoir room is connected via a hallway to a water source, leaving it blocked off by 1 square until I complete construction at which point I'll channel from above to let the water in. The hallway leading from res room to water source has a grate so nothing can enter my fortress from there, and a door (also attacked to a lever) so that I can cut off the main water source from my system.
I've attached a diagram. The c is where I channel when everything else is complete. The purple hatch marks are my grate. The green squares are doors attacked to separate levers. The down arrows are channels onto the next level that I use to control overflow.
During normal usage, door 1 is open and door 2 is closed. When I want to re flood my room (I have a lot of issues with dwarves not farming so I end up recreating my farms a lot and this seems to help) I just close door 1 then open 2. The water rushes into my room and floods it. Any excess runs off through my drainage squares to leave a quick drying farming area.
Let me know if you want to try this and have any questions.
/e: updated picture link and modified the intro a little for clarification
(http://i.imgur.com/brhGe.png)