I actually checked the shutter cover in game and it reads “Connects and disconnects pipes”
If it said it was also directional i would have suggested it. I didn’t know it was directional.
But now that you mentioned it, i remember a YT video on GT pipes and using the shutter covers to prevent fluids sloshing about.
Also, GT6 changelog:
[ADDED]
Shutter Cover.
It prevents Items and Fluids from going through, and is also able to connect and disconnect Pipes, Cables and Wires aswell.
Controlled by the Cover-Controller-Cover, and also has an inverted Mode. (With a bit of trickery on the inverted Mode, you could replace Wirecutting and Wrenching Stuff with Screwdriving it instead)
It doesn’t actually say anything about one way there either.