Cost Advisor

Noise in a water system (water hammer)

February 19, 2015

Sound is louder and travels faster in water than air. there are several causes of noise within a water system, including disturbed water as it flows through a pipe, faulty valves, or friction. the rougher the internal surface of a pipe, the greater the number of joints and the more acute angles within a system, then the higher the likelihood of noise.

The following are precautions which you plumber can take to help reduce the possibility of noise in pipe line:

  • Use a pipe with a smooth internal surface such as copper or plastic.
  • Avoid unnecessary joins. Ensure all cut ends are de-burred prior to completing connections.
  • Long radius bends are preferable to manufactured bends when changing direction. If the radius of the bend is not less than five times the diameter of pipe, the flow will not reduce.
  • Pipes are to be sized correctly to ensure that when water is drawn off, the rate of flow is below the maximum velocity for the pipe (which is generally 3m/sec).
  • Ensure all pipework is sufficiently clipped.
  • Humming or Screaming noises may be caused by a screw-down tap when the jumper spins. the edge of a worn washer may become serrated, causing the jumper to spin and the stem within the jumpers’s spindle creates the noise.
  • Chattering noises may be caused by loose parts such as jumpers in screw-down taps or pistons and lever arms n ball valves. Parts become loose over time and require servicing or replacing.
  • Limit the incoming pressure with a pressure limiting valve.


Water hammer is caused when a tap or valve on a water service is closed suddenly, causing a shock which can be felt and heard. When a column of confined water, travelling at speed, suddenly stopped, a great force is exerted. Water hammer has the potential to damage pipework and valves.

Areas of significance with water hammer problems include:

  • Solenoid valves (washing machines, dishwashers and zip boiling units)
  • Flush valves
  • Full flow ballcocks
  • Long runs of pipework
  • Ceramic disc tapware
  • Worn valves
  • Pumps

To fix a water hammer, a water hammer arrester can be installed as close as possible to the offending valve. A tee is cut into the pipeline and the arrester is screwed into place. The arrester is an air or gas charged chamber which will absorb the shock wave within the pipeline. The air or gas compresses, absorbing the shock wave, ans then releases the force.

Remember the above in only indicative information to your water-hammer problems. Several tests can be done to pinpoint water-hammer and accordingly several solutions are available.

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