What is water hammer?
Water hammer or banging pipes are differing faults with your water reticulation system.
In theory, you should never hear the sound of water moving through your hot or cold water pipes. All you should ever hear is the water flow from the tap or fixture in the room it’s installed in.
Essentially water hammer is a shock wave created inside your piping.
What causes water hammer?
Plumbing is essentially the movement of water through pipes. It, therefore, has the potential to be noise creating and create what is referred to as water hammer.
Water hammer that is noticeable occurs with copper water pipes. But plastic water pipes also suffer from water hammer, and it’s just harder to hear it.
Water hammer audible noise in copper pipes is generated primarily by:
High water pressure
Quick closing mixer taps
Quick closing solenoid valves
Faulty or worn brass seats in taps
Broken tap washers
Airlocks in pipes
Shock waves in pipes
Common noise complaints
There are four very common noise complaints with water pipe reticulation systems being:
Sharp banging or hammering sounds coming from pipes
A series of loud bangs when the washing machine or dishwasher is in operation
A loud bang from a valve or tap
Audible ticking sounds that diminish after the tap is turned on
An intense banging or hammering is a result of faulty valves, defective mixer taps, defective solenoid valves, broken taps or broken tap washers or poor clipping of pipes.
A series of loud bangs while you are using the washing machine or dishwasher is caused by the instantaneous opening and closing of the solenoid valves in the machine as it traverses through its cycle.
Excessive water pressure can accentuate all of these causes as water pressure legally cannot exceed 500kPa inside the building.
The ticking sound can build up then diminish and are in fact the sounds generated by pipe expansion. This is caused by the pipe heating up when the hot tap is turned on as the hot water replaces the cold water and then cools down.
Water hammer is a shock wave
Water hammer will occur much more if your pressure is excessive. The common causes of water hammer are quick closing mixer taps or solenoid valves on washing machines and dishwashers.
In the picture above the shock wave is generated at the face of a quick closing mixer tap because the flow of water moving under pressure is stopped suddenly by the instant turning off of the mixer tap. The shock wave then ricochets back from the face of the mixer tap cartridge, through the stationary water in the pipe. The shock-wave creates enormous pressure moving at 1280 meters per second through the pipe.
This same effect is replicated more intensely by the solenoid valves in your washing machine and dishwasher as unlike mixer taps they instantly open and shut as you machine moves through cycles.
Water hammer is an early warning alert
All of the sounds or the audible noise commonly referred to as water hammer tend to be highlighted in copper water pipes. Water hammer still exists in plastic piping systems, but it is diminished significantly as the plastic pipe absorbs the sounds.
Your plumbing reticulation pipes, taps, valves and appliances are all susceptible to damage caused by the impact of shock waves even if you hear no noise.
The noise is essentially an early warning system telling you to rectify the problem before damage occurs.
Water hammer is avoidable
Water hammer is avoidable and can be rectified regardless of whether you have copper or plastic water reticulation piping.
Banging or noisy pipes usually occur when the water reticulation pipes have not been clipped correctly as per AS/NZS 3500.1 : 2018 when the house was originally constructed. This can be much more challenging to rectify compared to water hammer.
To prevent damage to plumbing pipes, taps, fixtures, hot water valves and appliances both the noise element and shock wave element of water hammer need to be eliminated.
The noise element is auditory. The loud bang of water hammer when you turn off a tap or your washing machine is running alerts you to water hammer problems. Without the noise, there will be no indication of a problem until the damage is caused or your home is flooded by a burst flexihose or appliance hose.
The elimination of the water hammer eliminates the shock waves which impose undesirable stresses on reticulation pipes, flexihoses and appliances.