When I turn on the hot water at my kitchen sink, it makes a noise after the pipe heats up (about 10 seconds). The cold water tap doesn't make a noise. What could this be?

speedball1

As the hot water heats up the branch line the pipe expands against the pipe strap and the stud. You'll hear a tapping or a rapping noise from inside the wall. As the pipe cools down it contracts making the same sound. The only way to stop this is to shim the pipes after you open up the drywall. to most people this simply isn't worth the hassle. But Hey!! I just took the mystery out of the noise didn't I? Regards, tom