I bought a home that is 7 years old with the original hot water heater. We began hearing a low thump followed by clicking noise from the hot water heater a few months ago. It happens about every 8 minutes. Any time you use water, hot or cold, the hot water tank will click. The thumping sound, followed by clicks seems to occur when no wter is being used, like all night long! I discovered that if I shut off the cold water line to the hot water heater, all the sounds disappear. Do I need a new hot water heater, or will flushing it eliminate this annoying issue?