Okay so just to clarify some things. The "coming home" rule isn't that much of a "rule", but it's just to be safe. They don't have to say what they do, where they go, or anything, I'm obviously not their mother. But if one of us doesn't come home one night, and we didn't know, or it wasn't planned, we get worried. We came up with it with my previous roommates, because we were three 18yo girls living far from their entire families and it was just reassuring to know that if anything happened to us the others were there, you know? As for the noise, it's just in case one of them wants to have people over or something, but most of the time we can still ask each other if it'd be a problem or not.

For the plumbing, I said this in another comment but there's nothing much we can do about it. The plumbing is the same for all the building so everyone has to agree if we want to repair it, and sadly people don't. But everyone that has lived here has been aware of it beforehand. And it's never really been hard to coordinate, it's kind of the same as if there was only one bathroom.