Whnever the main floor toilet is flushed, there is banging noise is heard 25' from the toilet. 90% of the ceiling below the toilet is open, I cannot feel any vibration in the supply line when the toilet is flushed. I have pulled the PEX supply line out 12" at the toilet and know there are no obstructions to the line. I cannot figure out what the problem is. Has anyone lese had this problem and what did they do to fix it?

Thanks JimKup