These questions and answers are intended to clarify the rules of RoboRally. They are not meant to supersede or substitute the game rules. If any answer below actually modifies or corrects the original published rules, we will make that clear to you.
Since drains are functionally identical to pits, they should be treated as pits for all purposes; therefore you may place bridges over drains. Bridges may only be placed over troubled water, so you may not place bridges over other water squares.