I have to admit, it would be funny if, just one time, in a Trek ep or movie, we hear a toilet flush, and then we see a crewmember walking out of the head (Naval term for bathroom), or the flush and then the Captain walking out of the head in his quarters/ready room.![]()
Check out the seat Kirk is sitting on in the brig in ST V. The sign says, "Do not use while in Spacedock."
http://en.memory-alpha.wikia.com/wiki/Toilet