Unlocking the Sewer in Amnesia: The Dark Descent

[BendyBread]

In the "actual" cistern, there are 4 different valves (to the best I can remember). You need to turn all of them the whole way (they only turn one way), and you'll know they've been turned fully by a sudden gush of wind near you every time.

The steam requires a little timing, but it does stop after a few seconds. You need to ran past VERY quickly before they come back on. Their is a valve to turn the steam off, so on your way back you wont need to run past them.
Hope that helped.