What is water hammer?
Water hammer (sometimes erroneously called air hammer) is that banging noise you hear in the wall when a faucet is turned off abruptly. The source of the noise you hear is the piping moving laterally and striking the framing or wall surface materials inside the wall cavity. This condition often occurs with appliances such as clothes washers or dish washing machines that stop the flow of water rapidly. Another common location is at shower risers when a single handle fixture is in use that tends to “shear off” the flow of water when the fixture is turned off. To see a visual example of this phenomenon, turn on your garden hose with a self-closing handle nozzle. Hold your hand on the nozzle handle spraying full blast. Let go of the nozzle quickly. The nozzle shuts off, and the garden hose jumps around wildly. This same movement can occur in the wall when you hear piping noise caused by water hammer. The higher the pressure, the more hydraulic energy and the more noise you will encounter.
WATER HAMMER is the generation and effect of high pressure shock waves (transients) in relatively incompressible fluids. Water hammer is caused by the shock waves that are generated when a liquid is stopped abruptly in a pipe by an object such as a valve disc. Symptoms include noise, vibration and hammering pipe sounds which can result in flange breakage, equipment damage, ruptured piping and damage to pipe supports. Whenever incompressible fluids exist in a piping system, the potential exists for water hammer. The risks of water hammer developing are particularly high when the velocity of the fluid is high, there is a large mass of fluid moving and/or when there are large elevation changes within the piping systems. Since the swing check must rely on gravity and/or fluid flow to help it close, flow reversal must occur before closure begins. When the swing check finally closes, it abruptly stops the flow and causes a pressure surge resulting in shock waves. These shock waves continue u
Water hammer is a very loud banging, knocking or hammering noise in the pipes that occurs when the flow is suddenly turned off. It is caused by a pressure or shock wave that travels faster than the speed of sound through the pipes, brought on by a sudden stop in the velocity of the water, or a change in the direction. It’s also been described as a rumbling, shaking vibration in the pipes. You might hear water hammer when the clothes washer stops filling, the sprinkler system shuts off or shifts to another zone, when the dishwasher changes wash cycles, or when a faucet is turned off suddenly. It exerts very great instantaneous pressures that can reach excesses of 1000 psi and over time can potentially damage the system by weakening joints and valves causing leaks or even ruptures in the pipes. Several factors can contribute to water hammer such as: • Improperly sized piping in relation to water flow velocity • High water pressure with no pressure-reducing valve • Straight runs that are
Water hammer is a pressure shock wave induced in plumbing supply systems whenever there is a sudden change in the steady state condition of a non-compressible liquid such as water. Pumps, valves, faucets, toilets, and fast solenoid-activated valves (such as commonly found in washing machines and dishwashers) are all examples of devices that can induce water hammer within a typical plumbing system. Water hammer can result in noisy, banging sounds as pipes rattle and expand to absorb the pressure wave. Shock waves in typical water pipes travel at up to 4500 feet/second and can exert tremendous instantaneous pressures, sometimes reaching 150 to over 1,000 PSI. If left unchecked, water hammer can damage pipes, valves and eventually weaken joints. However, the lack of noise does not mean that water hammer is not present. Several factors exacerbate water hammer and are generally traceable to inadequate system design and installation. These include: • Improperly sized supply lines for given p
When a liquid is suddenly brought to rest within a piping system, by either a quick closing valve or a check valve, a shock load surge results, better known as waterhammer. The higher the liquid velocity and the longer the piping, the greater the effect of waterhammer. Due to its destructive nature, broken pipes, valves, fittings and pumps can result from waterhammer. Since the shock waves travel throughout the system, the results of water hammer are found in different parts of a system to that which caused the problem.
