Yesterday I woke up to hear what sounded like dripping water. Strangely this sound is audible at all water-outlet locations - bathrooms, kitchen and laundry area. It is a continual noise at about one second intervals. You can feel the vibration on the cold water line in sync with the sound. (No vibration on the hot water line.) I have tried shutting the valves (one at a time) at the toilets and sinks but with no results. The water pulsates as well. Could this be the pressure relief valve? I'm baffled. Any help would be appreciated!

Do you have a well or municipal water? What kind of plumbing? Plastic tubing? Copper? Flexible plastic (pex)? Iron pipe? Has it gone away by now?

We need more details.

Thanks for your reply. It is municipal water and copper tubing. The noise lasted for two days and then disappeared. So far... so good!