"Balneō lavor" should be added.
Or in balneo lavor?
Sure. In + ablative case, or just the ablative case, to mark location. Unless it's one of the words that still have the locative case in classicsl Latin, in which case that is used to mark location.
The English said I was myself in the BATH. Not the bath house. A bath is the same as a "tub", the thing you sit in to wash yourself. So labrum should be acceptable