When my heat (forced hot air) comes on for the first time in the morning, there is a loud "tapping" noise from the hot water feed to the unit in the attic. The plummer has added anti freeze but it still makes noise. He said it happens when the cold water is fed up to the heater. The pipes are the new plastic (sorry cant remember the name) and not copper. The pipes are not banging off the wallsjust a very loud tapping noise - loud enough to wake us up every morning when the heat goes on.
Any help would be appreciated