Originally Posted by 1stTimeDIY
the toilet in my boys bathroom runs a little bit any time i use any water anywhere else in the home.
So the tank water level drops when the system pressure drops. This is a new one on me. By default I'd guess a defective ball cock mechanism but I can't explain how.
Maybe that toilet always runs slightly and a pressure drop makes it more noticeable. At least this way the incoming water is "connected" to the system pressure because the ball cock valve is slightly open.