At some point, every day, my kitchen sink totally loses water pressure. This can happen 2-3 times in a single day. It can have great pressure one second, and be drip dry the next second. It doesn't necessary seem to be related to using other faucets in the house. After it goes dry, if I leave the tap on long enough, sometimes a couple hours, a drip, drip, will turn into a small stream of water and eventually I have full water pressure again. I'm on city water so it's not a well issue. How can air be getting into the water line?? Does anybody have any ideas on what could cause this??