If you have a place with enough population to be called a city, then you really need a lot of brick outhouses. I almost used a word that some might find offensive, but I know that you know what I mean, eh?
Good point, 2 million Israelites, common commodes, probably went in clay jars which were tossed into the Nile -- orrrr, like other cultures, it got mixed into the mud bricks. Might be interesting to break one apart and check for DNA and other biological frags.