My girls drink a lot, too. I just responded to another thread asking kinda the same question, so I'll put my same response here.
The other thread:
http://www.rabbitsonline.net/view_topic.php?id=26177&forum_id=1
My reply there:
From what I gather, my girls drink a lot, comparatively.
They each have 32oz water bottles. Trixie finishes hers in about a day and a half, Flower about every two days, Maisie and SweetPea about every two and a half days.
Trixie is 9lbs, Flower 7lbs, and Maisie & SweetPea are both approximately 5lbs.
So, yeah, depends on weight...and I don't think anything's wrong with them drinking a lot. I know for a fact that my girls are healthy, and I think the vanilla we put in their water lends to them drinking more.
In fact, when we got SweetPea, her mama let us know that she drank about an eighth of her 32oz water bottle a week, and she's been drinking MUCH more than that while being with us. So, yeah, I think the vanilla has a lot to do with it.
BUT...two things...
Has their fluid intake changed recently, or is this their normal intake?
What are your buns' sizes?