Unlocking the Sewer in Amnesia: The Dark Descent

[deathrider]

Okay, so I'm playing Amnesia and I ran into a problem -- I can't get to the Sewers. Whenever I try to go down, the water gets too deep and some text comes up on the screen and says that I can't go any further down the stairs.

I'm in the Cistern area.
I've been in every room in this area, all of the puzzles have been solved (as far as I know).
I went into the Control Room and readjusted all of the weights and mirrored them to the ones across the room, then went into the back room and placed the pipes where they should be and adjusted the levers to the "down, up, up, down" sequence.
I went into the Morgue and drilled a hole into the dead guy's head and placed the needle there, and left the room after the Brute did.
In the actual Cistern room, I threw a rock at the bridge and it fell down so I crossed it and turned the valve.
Now here's my problem. I'm playing this game on my brother's account at his house, and I don't know if he didn't turn all of the valves the right way or not, but I remember him going past those steam pipes and turning the valves there and screwing with the valves and levers in that whole room. I just tried crossing again but the steam pipes won't stop even for a second and I've been sitting here waiting for god knows how long.

I've double checked everything and I don't know what I could be missing. Can anyone help me?

Thanks in advance. (: