Water Heater Piping Noise I have a gas water heater and furnace in a condo unit. I have been hearing what I would call "clicking" noises when the furnace and water heater run. The noises almost sound like water hitting ducts. This could be it ...but ... The noise comes from below through the floor and about 12 feet away from the furnace and water heater ...right before the bathroom. I put my ear down on the floor to listen to the noise. The noise sounds almost as if it has a recoil on it. Like it makes the noise hitting ...then makes a small noise going back. They are semi-random and I "believe" it is mainly from the water heater being on. The noises only happen when appliance is running. Any guesses?