He who pisseth against the wall such as in the house of Ahab would be all the males. The women are left alone.
As for which wall, I wondered about that myself. It would really be a stinker should it be a special wall somewhere. And how do you take a Number Two?
I would not call it a bathroom. Quite certain baths were poured in a separate place. Imagine reaching for a bar of soap (if they had soap) with one hand and pinching your nose due to a stench with your other.

The word "white wash" just occurred to me as future possibility.