We have a clicking sound that happens when we run hot water in several bathrooms, kitchen sink and dishwasher. It does not appear to happen when running water in the bathtubs or showers (or maybe we just can't hear it because we are singing too loudly). Seriously, it sounds like the pipes will bust open and we can follow the sound along the wall where the pipes likely run. The plumbers who "fixed" our frozen pipes (see other post today) listened to this sound, and said they didn't know what could cause the sound. Any tips before we pay plumber #2 to come out and assess the situation? Much appreciated. I realize it *could* be one of several things, but what is the most efficient way to find the problem and fix it before it really does become a mess? Much appreciated.