How to Fix a Water Hammer

Water hammer is a home water pipe problem that is irritating and, if not repaired, can cause serious damage to the home's plumbing system. When you hear the water hammer for the first time, you will know that something has gone wrong. This banging or hammer noise may be noticed when a dishwasher, toilet or faucet shuts off the flow of water. You may notice it as one loud bang when you shut off a faucet quickly, or as a series of bangs or hammering sounds when a water closet is filled and shuts off slowly.

Difficulty: Moderate

Instructions

1. 
    
   Main Shut-Off Valve

   Shut off the main water supply where it comes into the house from the outside supply. This is usually accomplished by turning the faucet control clockwise. Be sure the water supply has been completely turned off.

2. 
    
   Sink

   Open faucets in sinks, showers and bathtubs. Make sure every faucet has been opened. Start with the faucets on the lower level or basement of the house. Then go to the next level and open each faucet.
   Let the water drain completely from the pipes. Remember to flush toilets to empty their tanks. Check each faucet and water supply to make sure the water has completely drained from its supply pipes.

3. Turn off all faucets after the water has been emptied from the pipes. Turn on the main water control valve. Turn on a faucet on the upper level and allow the water to run until all air has emptied out of the line. Turn that faucet off. Proceed to each faucet on the upper level and lower level, and repeat this step until every faucet has been turned off and air drained out.

4. Check to see if the hammer problem is solved by opening a faucet all the way and shutting it off quickly.

5. 
    
   Water Pressure Control Valve

   Listen while flushing the toilet or running the dishwasher or clothes washer to see if you hear any banging or thumping noises. If you do, you may have to replace the pressure control valve.

Tips & Warnings

• Look at water pipe hangers and check them for tightness. Loose hangers allow the pipes to vibrate and make noises. The pressure may be reduced temporarily by turning the main water shut off valve down one or two turns, reducing the pressure of the water coming into the house. This may work to stop the water hammer noises until the pressure valve can be replaced.
• Note any leaks or corrosion at the main shut-off valve that might cause problems now or in the future.

References

• More water pipe noise suggestions