You need a water hammer arrestor in your water piping system if you hear loud bangs in the pipes when you turn on the tap. The air vibrates against the pipes when water valves are closed, then opened. You can obtain all the materials you need to install a water hammer arrestor at a building or plumbing supply center.
Step 1: Determine Where to Install the Water Hammer Arrestor
Find the area of the system where the water hammer is occurring. It will be in either 1/2 inch pipes or 3/4 inch pipes. Measure to be sure you get the correct-sized water hammer arrestor and T pipe, then purchase the materials.
Step 2: Prepare to Drain the Pipes
Shut off the water supply for just the area where you will install the water hammer arrestor. If you can't shut off part of the water supply, turn off the supply to the house with the main water shut-off. Turn on the taps at the fixture which has the water hammer.
Step 3: Cut the Pipe
Cut through the pipe 12 inches from the valve or T pipe on the side leading to the fixture, away from the primary water flow pipe. As you cut through the pipe, have the bucket handy to catch the water that will drip out. Once you have cut through the pipe, drain out all the water in that pipe section.
Step 4: Splice the Pipe
Once the water has drained, cut another 1/2 inch off each end of the pipe you cut through. Sandpaper the new ends of the pipe until they gleam and are very smooth. Use the fittings brush to polish the ends of the T-pipe, the ends of the 2-inch-long pipe section and the water hammer arrestor. Brush a thin coat of solder flux paste onto the ends of the T-pipe, the cut pipe, the 2-inch section and the water hammer arrestor.
Step 5: Connect the Water Hammer Arrestor to the Pipes
Connect the ends of the water pipe to the T-pipe's arms, and insert the 2-inch-long copper pipe vertically into the T-pipe's outlet. Insert the base of the water hammer arrestor into the 2-inch pipe, so it is vertical.
Step 6: Solder All Connections
Put on goggles and apply solder with the propane torch to all the joins of the water pipes at the T-pipe. Solder together smoothly the T-pipe, the 2-inch copper pipe and the water hammer arrestor. Allow the soldered areas to cool for at least 15 minutes. Use a damp, clean cloth to wipe off excess solder and flux paste.
Step 7: Test the Water Hammer Arrestor
Turn the water supply back on and test the water hammer arrestor, while checking for any water leaks. If the joins leak, drain out the water again and apply fresh solder. If you still hear water hammer, another water hammer arrestor is needed elsewhere in the pipe system.