Exploring the subterranean Boilerworks on floor B2 of Luigi's Mansion 3 offers players some of the most clever environmental puzzles in the entire game. Amidst managing complex water valves and shifting platforms, tracking down the six hidden collectible stones requires an observant eye and creative use of Gooigi's unique abilities. Securing these treasures ensures complete exploration of the damp depths while boosting your overall achievement rank.
Discovering the Early Valve and Pipeline Gems
The first collectible can be uncovered shortly after entering the main reservoir area where massive water pipes block immediate progress. Luigi must utilize the Suction Shot to remove a loose metal panel on the far left wall, exposing a hidden pipe line. Sending Gooigi through this pathway allows him to drop directly onto a secluded shelf containing the red gem.
Further along the watery pathways, players will encounter a rotating valve mechanism that controls the local water levels. By turning the handle to drain the immediate chamber completely, a hidden floor grate becomes accessible near the lower platform. Gooigi can slip through this drainage point into the undercurrent area to secure the green gem resting behind a cluster of weeds.
Navigating the Subterranean Storage and Cage Puzzles
Deep within the storage rooms, a large hanging cage serves as a distinct environmental puzzle that requires seamless cooperation between both characters. Luigi needs to locate a heavy stray brick nearby and vacuum it up to launch it directly into the open cage structure. The added weight drops the container lower, allowing Gooigi to walk across the top beam and fetch the blue gem from a high pipe junction.
As you progress toward the main elevator shaft, look closely at the brickwork along the northern hallway corridor. There is an obscured alcove hidden behind a stack of old wooden crates that can be shattered with a burst from the Poltergust. Behind these obstacles lies a glowing spectral object that reveals the yellow gem once hit with a bright flash from your Strobulb tool.
Unlocking the Final Hidden Vault Treasures
The remaining collectibles require backtracking through previously flooded chambers after the main water supply has been permanently rerouted. In the central control room, a seemingly non-interactive computer terminal features a small circular slot perfectly fitted for a suction cup plunger. Pulling this lever activates a secret wall compartment on the right side of the desk, dropping the purple gem onto the floor.
The final clear gem is cleverly hidden inside the main sewer junction where the boss fight takes place. After defeating the watery threat, look toward the southwestern corner of the arena to spot a loose metallic pipe sticking out of the floorboards. Using the Poltergust to blow a continuous stream of air into the pipe will launch the final stone directly into the air for easy collection.
