I want one of the on demand ones, but they're quite pricy and I can't get my husband to agree with me. They do save you money, though.
As to the OP, this is one of the reasons I'm going to ask my husband to switch around the way the bedrooms are in the house: I want the kids to be upstairs and us downstairs. I can then put my darkroom/office in what is right now my daughter's room, and I won't have the issues I'll have if I have to be down the basement.
I need an office with water anyway. I dye yarn. It'll be nicer to have a room that is dedicated to my arts/crafts than trying to have it all over the house.