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

[Apjjm]

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.

There are certainly 3 you need to rotate:

Spoiler below!

Quick note
You can see which valve you have yet to turn as after turning each valve the lights in that area are extinguished. Take the path with the lights that aren't extinguished and turn that valve off - as that is the path you have yet to complete. If I recall correctly, the valves you want to turn are all numbered, and some have notes and diary entries next to them.

Where each path is
Facing the direction from where you enter the paths are:
To the left:

• Knock down the bridge
  
• Navigate the walkway and the rubble
  
• Valve should be waiting to be turned
  

To the right:

• Go up the stairs then straight ahead until you can go no further
  
• Turn left and the valve should be waiting
  

Straight ahead:

• Get past the steam
  
• (Optional) Turn the steam off with a valve (This is a different valve!)
  
• keep going along this path and the valve will again be at the end.
  

If you are certain you are stuck and the game has glitched here I would advise doing the other areas in the cistern and posting up your save file, so I (or somebody else here) can attempt to finish the puzzle, or provide you with a fixed save.