First Floor: There are restrooms located next to the Starbucks entrance closest to the main library entrance, and also some located on the back hallway on the first floor. If you follow the hallways past the Public Services Desk to the end, you will reach the back hallway and the restrooms are located on the wall across from the study table.
Second/Third Floor: There are restrooms on these floors located directly above the restrooms next to Starbucks on the first floor.