How do I avoid the acid bath

Hint 1 of 5:

You need a friend, but not a janitor's friend.

Hint 2 of 5:

You need a plumber's friend, a plunger.

Hint 3 of 5:

Find it in the janitor's closet on floor three.

Hint 4 of 5:

Stick it on the wall as the floor opens, and hang on.