[SPOILER] Stuck on Cistern stage; valves won't budge

[gregarious24]

Spoiler below!

There are three valves you need to rotate, in case you missed on of them

Hmmm. Perhaps I haven't made myself clear, but the person who uploaded that walkthrough video only needed to rotate two valves in order to drain the sewer, excluding the steam shut-off valve. I've rotated those same valves (they won't turn at all anymore), yet my sewer still is not drained.

I've reexamined that walkthrough vid from the very beginning of this stage and have re-traced my steps in full, but I simply cannot find a way around this problem. If anyone knows specifically where I'm going wrong, please don't hesitate to spell it out for me.

EDIT: Just wanted to give thanks to jens / Frictional. Amnesia's the first game to keep my attention since Half-Life 2. Much appreciated.