What Should I Know About Water Hammer? | The Plumbing & Electrical Doctor

What Should I Know About Water Hammer?


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You know that irritating, loud, banging and vibrating noise that you hear when you turn off the tap? It’s what we call a water hammer.

Water hammer occurs when a valve is suddenly turned off which causes the pressure from the gushing water to suddenly stop. This high pressure then causes hydraulic shock waves that reverberate throughout the pipes thereby causing those loud vibrating noise that you hear.

We would need to differentiate though if the sound that you hear is from a water hammer or from trapped air inside the pipes. One simple way to do this is to determine when you hear the sound. If you hear the sound after you have turned on the tap, then that is trapped air inside the pipes. But if you hear the sound after you have turned off the valve, then definitely that is a water hammer.

Water hammer may only sound like a simple annoyance but we should not take it lightly. Water hammer can lead to a serious plumbing issue and can lead to a leaking pipe or burst pipe. The most common valve that causes water hammer to occur in your homes are the valves in your washing machines and dishwashers. These valves were designed to deliver more than the usual amount of water to the water fixture that they are connected which means that there is a higher water pressure coming from the flowing water on these taps. So when you suddenly close these valves, you now have the recipe for a potential water hammer.

Normally, when you shut off your valve or close the taps, the water pressure is diverted into the air chamber on the vertical pipes to cushion the effect of the water pressure rushing in when the water is suddenly shut off. The vertical riser, therefore, helps to minimize the water pressure and dissipates it before it reverberates throughout your piping system. But over time that air packet is lost and that’s when a water hammer occurs.

In order to resolve and fix any water hammer issues, you would need to restore the air packet on the vertical risers on your taps. You can try fixing this by opening the highest tap in your house and let it run for a while in order to remove the air inside the pipes. 

If this will not resolve the problem, you can try shutting off the main water meter and letting all the water drain from your property. Once you turn the water back on, this would let air back into the air chambers on the vertical risers of your piping system. If the water hammer is caused by very high water pressure, you would need to install a pressure limiting valve so as to control the water pressure going inside your house.

What are the types of pressure limiting valve available in the market?

  • Direct-acting – The simplest of PLVs, the direct-acting type, operates with either a flat diaphragm or convoluted bellows.
  • Internally piloted piston-operated – This type of PRV incorporates two valves-a pilot and main valve-in one unit.
  • Externally piloted – In this type, double diaphragms replace the piston operator of the internally piloted design

It’s best though to do preventive measures in order to prevent water hammer from happening in your piping system. One way is to replace your flick type taps that close very quickly with the soft close taps. Another way is to install water hammer arrestors. They might be costly though since you would need to attach them to all your mixer taps.

Water hammer can cause pipes to burst and leak so if the problem persists, it would be best to call your local plumbers to check on the problem before it gets worse.

Plumbing Repairs | Plumbing and Electrical
Pressure limiting valve installation using a B-press machine
Water Tank Parts | Plumbing and Electrical
Water hammer arrestor

 Here is another article that you may find interesting in regards to “Why do my lights flicker?”.

If you got any electrical and plumbing problems don’t hesitate to call us at 13 10 91 to fix the problem right away. We serve areas in Newcastle, Canberra, Central Coast, Hunter Valley, Lake Macquarie, and Port Stephens.

At The Plumbing and Electrical Doctor we have made these articles downloadable to PDF for our customers convenience.

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