Main Tank

The Main Tank is a location in Luigi's Mansion 3. It is found in the Boilerworks, located north of the Reservoir.

When Luigi first arrives the Main Tank, he encounters Clem sleeping at its top level. Luigi attempts to avoid waking him up again, only to end up stepping on another rubber duck, awakening him yet again. An irritated Clem then tries to prank Luigi one last time by filling the Reservoir. However, after Luigi rides an inner tube shaped like a duck, saves himself, and reaches the top using the rising water, Clem decides to confront Luigi personally. During their battle, Luigi ultimately defeats Clem before proceeding to drain the tank to collect the Tomb Suites' elevator button.

When Luigi visits the Main Tank again, a Boo can be hiding.