How To Fix Toilet Water Hammer

Posted on: 10 October 2016

If you hear a banging sound after flushing the toilet, it is likely water hammer. Water hammer occurs when air gets compressed in the system, causing water to hit the pipes.

The problem should be fixed right away to avoid pipe damage. A beginning DIY person can fix water hammer with basic tools. Here are tips to fix water hammer after flushing a toilet.

Prepare to Work

For this project, you need:

  • work gloves
  • safety goggles
  • tape measure
  • sponges
  • rag
  • drinking glass or bowl
  • adjustable wrench
  • 220-grit and 400-grit sandpaper
  • hacksaw or pipe cutter
  • water hammer arrestor kit

Turn off the main water supply to the house, which is a valve on the water line close to the water meter. Rotate the valve clockwise.

Flush all toilets, and turn on taps to relieve water pressure. Sponge excess water in the back of the toilet.

Wait fifteen minutes, then shut off the water supply to the toilet. The water supply valve is commonly beside the toilet close to the wall. Turn the valve to the right to shut off water.

Clean the Toilet Tank

Sometimes, dirt in the toilet tank can cause water hammer. Disconnect the top of the fill valve to reveal the supply line. Turn the water on, and set a bowl or glass underneath the open end of the fill valve to catch water.

Use the rag to clean the exposed end of the fill valve. Flush the toilet several times to release dirt. Shut off the toilet water supply, and reinstall the top of the fill valve. Restore water, and see if it stopped the water hammer.

Install the Water Hammer Arrestor

Buy a water hammer arrestor to fit the size of the pipe. Set a bucket under the pipe to catch water as you cut it.

Use the hacksaw or pipe cutter to trim a piece of the pipe to fit the T-fitting on the arrestor. Leave a half-inch of pipe sticking out from the wall. Smooth burrs with 220-grit sandpaper, and clean sand dust with a rag. Sand again with 400-grit sand paper.

Insert one end of the arrestor into one exposed end of the pipe. Clean sand dust. Use the pipe fitting brush to polish the ends of the pipe section and the T-fitting ends.

Insert the arrestor into the pipe. Keep pressing the arrestor in the pipe until you hear a click or a snap. Repeat on the other end of the pipe.

Turn the water back on, and flush the toilet to test. If the water hammer doesn't stop, or you don't trust your skill, contact a plumber.