A Tapping Noise in the Pipes When the Hot Water Heat Comes On

Water Hammer

• A water hammer happens when you suddenly turn off dishwashers or clothes washers. This forcefully shuts off the high-pressure water. In turn, the pipes may rattle and make a loud banging or tapping sound, known as a water hammer. Because water from both the cold water system and your hot water system feed these appliances, you might associate the water hammer sound with your hot water heater. Installing code-required, T-shaped air traps along the hot water line can help to remedy this problem.

Pressure

• Extremely high pressure in your hot water supply can create a loud tapping sound when your hot water comes on. The water pressure should be no higher than 50 pounds per square inch, according to how-to author Bill Marken. If you have excessively high water pressure, consider having a plumber install a pressure regulator on your water supply.

Water Heating System Sounds

• If you have a radiator that uses a boiler to circulate hot water throughout your home for heating, you might hear a tapping noise. The tapping happens when the metal pipes in your radiator expand as they get heated from the hot water flowing through them. This can cause them to tap against the sides of the radiator. Add extra padding around the pipes in your radiator to solve this problem.

Copper Pipes Through Wooden Frames

• Copper pipes carrying hot water should not be loosely installed in your home. If copper pipes move through the wooden frame of your home, they can tap against the wood when they expand with hot water flowing through them. Check pipe straps or hangers and add foam insulation around pipe that runs through walls.