Water hammer – pipe rattles

Water Hammer – Pipe Rattles

Water hammering or water surges can drive a home owner crazy. Water hammer sounds like someone in a haunted house is banging on the pipes with a hammer. Many times these noises are most noticeable at night or when the home is quiet. Some homes only experience the problem during periods of higher than normal water pressure from the street such as in the middle of the night or if there is a fire in town that causes the municipality to turn up the water pressure in the street.

Water hammering noises in plumbing are also called hydrostatic shock. Water hammer noise suppressors are one way to help cure the problem They are designed to be added to a washing machine hose connection by a homeowner, in order to avoid having to cut and solder pipes.

We find water hammering or banging pipe noises in buildings into two categories:

  • Water hammer noises in house plumbing systems, typically water supply piping
  • Banging heating pipes heard mostly on steam heating systems but occasionally (more creaking and cracking noises) on hot water heat systems as well

Water hammer is a noisy pipe problem that occurs when valves are shut off quickly. You may hear them in the water piping when a plumbing fixture, sink, or clothes washer turns off. Water hammer can damage pipe connections and result in leakage. Since water is essentially incompressible, large pressure is built up against the valve. There is low pressure upstream in the pipe. The high-pressure of water wants to flow to the low-pressure area. This happens so quickly that a small vacuum is created against the valve as the water moves away from it. Water hammer can result in loud noises in supply plumbing pipes. They only occur as valves are closed. If a valve is closed slowly, the noise does not occur. One can be sure that water hammer is the problem. Water hammer is common with quick-closing electrically operated valves on appliances such as washing machines and dishwashers. Often air chambers are installed to control water hammer.

Let us sum up the causes of water hammer.

  • Excessive building water pressure
  • Poorly supported water supply piping
  • Certain fixture valves and controls may be prone to causing water hammer as they shut off high velocity flow very quickly
  • Water piping that is too small for the flow rate of water through the building piping.
  • Missing water hammer noise suppression device or air riser to absorb the shock of change in water velocity when water is suddenly shut off

The cures for Water Hammer:

  • Try draining the building water supply piping: if your building supply piping includes one or more air risers – vertical water pipes that end in a cap or stub – you may be able to stop water hammer noise by draining the building piping.
  • Try adding a water hammer arrestor or noise suppression device sold at building or plumbing suppliers. Install the water hammer arrester at or close to the plumbing fixture or faucet that seems most to cause the water hammer noise.
  • Check the building water pressure: if the building water pressure is too high, water hammer noise may be more likely.
  • Check the support for building water supply piping: water pipe noises may also be due to excessive movement, if your water supply piping is copper or another metal.

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