All Slatten Dale Pneumatic Tube Locations

Pneumatic Tube 1 - Bunker L7: Head to Bunker L7, located west of the southern entrance to Slate Mine Caves. You'll see it on top of a broken bridge. Climb the makeshift steps on the bridge, then make your way north to the bunker itself. Once inside, go north again and head up some stairs. The tube is in the eastern room, on the northern wall, right across from a desk. Keep an ear out for a Feral to the west of the stairs; they can make you infected, which isn't ideal on your first playthrough.

Pneumatic Tube 2 - Bunker L5 (Outlaw Camp): This one's nestled under the Outlaw Camp at coordinates 31.8E, 75.4N. It's a bit of a gauntlet because of all the Outlaws patrolling the area. Your best bet is to clear the camp first, as they won't respawn. To get to the tube, go to the lower part of the camp by taking the stairs down next to the Radio Tower. Take a left, then another left, and walk to the end. The tube will be against the left wall. Even if you try to sneak around the camp, you'll still have to deal with the Outlaws guarding the tube's location.

Pneumatic Tube 3 - Bunker L6: You'll find this tube shortly after entering Bunker L6, which is at coordinates 26.5E, 77.1N. This bunker is northwest of The Waterwheels. Once you're inside, just move forward a bit and hug the right wall. The tube should be right there.