I was afraid this topic would come up at some point
There may be evidence to the contrary, but is it not possible that vampires in DS go to the bathroom? After all, as a vampire Barnabas drank (booze included), ate, and had a heartbeat. I see no reason why the "old house" would not have had a "portable" bathroom (guess what one of Willie's jobs would have been?
) somewhere, just like much smaller houses with no plumbing had. Also, winter climate would have necessitated it.
As for Adam, I can't bring myself to answer further...