Puzzle:Underground Water Treatment Plant

After escaping being burned alive, you arrive at a large underground waterplant with multiple issues that can be optionally fixed before proceeding.

Solution

 * After escaping the fire, you'll enter a large hall with 4 pumps. Go up the stairs, turn left and keep walking until you find a monitor that should look like this;




 * Turn around and walk over to the fire exit door. On your way, turn all the pumps off using the buttons.




 * Walk through the fire exit door and enter the locker room. Grab the green card and enter the office building through the leftmost door.




 * There is a men's toilet immediately to your left. Enter it and retrieve the yellow keycard from the toilet bowl. Be careful not to flush the toilet, or you will have to load your last save.




 * Exit the toilet and reset the fire alarm using the panel to your left.




 * Go up 1 fight of stairs and enter the control room. Grab the keys from the desk.




 * Go up another flight of stairs and enter the office directly in front of you. Grab the orange keycard from the table to the right.


 * Return to the ground floor and exit through the door next to the fire alarm panel. Walk to the left until you find a gap in the railing with a ladder.




 * Climb down the ladder, turn left and carefully work your way along the ledge until you find a ladder.




 * Climb up the ladder and enter the secret room. Open the Sewer Pipe 03 valve (left) and close the Flocculation Pool valve (right). Then retrace your steps back to the catwalk with the gap in the railings.




 * Turn left, walk up the stairs and keep walking until you find the Raw Water Pool door. Enter it.




 * Open the Raw Water to Coagulation (left) valve:




 * Retrace your steps back to the gap in the railings and keep walking. Go down the stairs and press the Flocculation button.




 * Return to the ground floor of the office building and walk through the door at the back-right.


 * Walk down the stairs, turn to the right and walk through the gate. Close Sewer Pipe 01 (left) and open Sewer Pipe 02 (right).




 * Retrace your steps a little, and keep walking until you pass the sewer pipes shed. Turn left and keep walking until you find the Sedimentation door on your left. Enter it.




 * Walk down the stairs and open valve 2. All valves should be open in this room now.




 * Pick up the valve to your right and walk back to the sewer shed. Insert the valve, open it, turn around and activate the pump.






 * Leave the shed and partially retrace your steps to the Sedimentation room until you see the hatch with... tomato sauce? next to it. Enter it.




 * Climb down the ladder and open the Flocculation to Sedimentation valve:



You have now fixed all the problems at this plant and you should receive the Reserve achievement.


 * Finally, exit with the minitrain: