The Pressure Valve can be taken after you’ve found all six pedestal items. You can find it around the left side of the projector room, where you picked up the Bendy plushie.
All right, in order to get to the pressure valve, leave the pedestal room, take the left hallway all the way down, then continue the long hallway until it branches to the right, and keep going until it turns right again. You’ll enter the projector room, which will turn on and you’ll find a happy-dancing Bendy on screen.
At the end around the left is the pressure valve.
In case you’re interested in some nom noms, there are 3 Bacon Soup cans on the top shelf in the room.
When you turn the valve, the room will partially fill with ink–perfectly normal.
To get back to the pedestal room, follow the long hallway, past the tape recorder on the table, past the smiling cut-out of Bendy, and the room’s on the right.
Pull the main power switch.
