I have a toilet that every so often will not refill with water in the tank. I decided to work a little bit backward, and wanted to see if the turn off valve was working properly. So, first I turned off the water, then I unscrewed the entire turn off valve mechanism from the copper pipe leading from the wall. I then had my wife turn on the water supply from the basement to see if water would come out of the copper pipe. Much to my dismay no water flowed out! I am assuming the copper water supply pipe is plugged? How does that happen? Is this something I can fix by snaking some type of wire or should I have a professional do the job? Thank you for your advice.