When I turn the hot water on in the kitchen sink there is a hammering sound in the hot water pipes. It doesn't happen when I turn on the cold water. I got under the house and I can feel the vibration in the pipes. The house is about 30 years old and it just started making the noise. No plumbing work has been done on the house in the last 2 years when a cold water pipe (copper pipe) had a pin hole in the pipe.
Jeff