Pipe Room

The Pipe Room (Japanese: 配管室 Piping Room) is a room explored in Area Four of Luigi's Mansion.

Story
After obtaining the key from the Armory, Luigi can access this room. Upon entering, a cluster of green Flying Fish will spawn and begin attacking the ghost hunter. In the midst of the brawl, Red and White Grabbing Ghosts appear as well. After capturing all of the ghosts, the Pipe Room will become illuminated, but Luigi does not receive a Key. A barrel emitting an icy mist will release an Ice Elemental Ghost if Luigi approaches it. Once he captures it, Luigi can use the Ice Element to freeze the river of water flowing through the room. Once a makeshift ice bridge is formed, Luigi must turn a red valve on one of the pipes to stop the waterfall on the other end of the room. There, a key to the Cold Storage materializes, allowing the plumber to continue on his quest to find Mario.

Description
The Pipe Room is pretty filthy, containing an ancient crate, a bucket, and the aforementioned frozen barrel. The river of water is untouchable until Luigi freezes it.

PAL Hidden Mansion
The Pipe Room in the PAL Hidden Mansion is a lot harder than in the normal version, as the ghosts attack in waves. The first wave consists of three Purple Punchers and two Purple Bombers. While the Purple Bombers aren't that difficult to deal with, the Purple Punchers could get annoying. The next wave is two Red Grabbing Ghosts, and three Blue Twirlers. Once Luigi captures all these, the room will be illuminated.

Trivia

 * The Pipe Room and the first floor Washroom are quite possibly the only necessary rooms in the game which are never required to be lit up (unless of course the player is trying to catch all fifty Boos), as Luigi can completely ignore the Grabbing Ghosts, freely freeze the river of water and turn the waterfall off to obtain the key to the next room.