What is water hammering?

Have you ever heard a sound coming from your pipes that sounds a bit like jack hammering? You may hear it after you turn a tap off, or once a washing machine or dishwasher cycle has finished the water intake or fill part of its cycle. It is often a loud bang in your pipes after a fill valve or a shut-off valve shuts off.

Water hammering is how plumbers describe the banging sound that comes from your pipes or plumbing work. It might also sound like a knocking or banging on the pipes. The technical name for it is hydraulic shock, but most people refer to it as water hammering. 

What causes water hammering?

The hammering sound is caused when water stops or changes direction suddenly. The sudden stop in flow or direction causes the pipes to move and strike against other pipes, plumbing components or framing parts.

Water hammering can cause damage to your pipes and other plumbing components. It can cause pipes to break and plumbing joints to loosen, which could then cause further damage or leakage. So it’s essential to have the problem looked at as soon as possible.

What can be done about water hammering?

If you hear any banging or knocking sounds coming from your pipes – even if it’s just a faint hammering noise or any other subtle sound that doesn’t seem right – get in touch with us at Sumich Plumbing. We can have a look and fix the problem before it becomes worse, rather than waiting until you have more extensive, expensive problems to fix.

There are a few things we can do to repair water hammering.

Regulate the water pressure

Sometimes water hammering occurs because the water pressure in the house is too high. You’ll hear people talk about water pressure using the terms psi or kPa. These are the abbreviations for the units of pressure, kilopascals (kPa) and pound-force per square inch (psi).

What’s the difference? One is metric (kPa), and one is imperial (psi). In New Zealand, we use kPa.

To convert from one measurement to the other, we multiply the number of kPa by 0.145. To make this a bit easier, let’s use a multiplier of 0.15 so we’re using clean numbers we can multiply easily (1 kPa is equal to 0.15 psi; 100 kPa is equal to 15 psi, 200 kPa is equal to 30 psi, etc).

According to Watercare, mains pressure water is provided to homes in Auckland at a minimum of 200 kPa. In some homes, the water pressure can be much higher – even up to 500 kPa.

So, if you hear banging in your pipes and suspect you have water hammering, one of the first things we’ll do is check your water pressure. If it’s too high, we’ll reduce it slightly to stop the hammering. We do this by installing a water pressure regulator. Don’t worry – we’ll reduce the water pressure slightly so that the banging is gone, but you won’t notice a difference in your shower or washing up.

Secure any loose pipes

The hammering sound is often caused by pipes banging with the “shock” of water stopping because the pipes are no longer securely fitted. They either weren’t installed properly (very common with DIY work), or they have come loose over time.

We can secure the pipes by tightening or changing the pipe straps or hangers that hold the pipe in place. If needed, we can also pack foam pipe insulation around the pipes to absorb the sound or “shock” of the movement of the pipes. Packing insulation around the pipes is often an easier way to reduce the shock and noise if the pipes are in a tight or tricky spot where it’s difficult to reach the pipe strapping.

Install an air chamber

Another way to repair the water hammering is to install an air chamber. This is sometimes also called a water hammer arrestor. It is a small section of vertical pipe that creates a small air pocket near where the water hammering is occurring. The small air-filled pipe provides a cushion for water to rebound into when it changes direction suddenly. The air in the chamber compresses temporarily and absorbs the shock that would otherwise go into the pipes and create the “shock” or banging.

The Sumich Plumbing team can install an air chamber if we determine that it’s the best method for repairing the water hammering you’re experiencing. It’s best to have a registered plumber install an air chamber as there is the risk of further damage if they’re not installed correctly.

To find out what is causing water hammering in your pipes, and determine the best way to repair it, give the experienced team at Sumich Plumbing a call. 

Get in touch for a no-obligation quote.


There are a number of plumbing and drainage companies in Auckland, so why choose Sumich?

Founded by owner-operator Chris Sumich in 1991, Sumich Plumbing & Drainage has one of the most experienced teams operating in Auckland. Our team has a combined experience of over 100 years and we’ve seen a comprehensive range of scenarios and solutions over the years. Clients trust us to give honest, transparent advice and service.

As registered members of the New Zealand Plumbers, Drainlayers & Gasfitters Association, we are professional, licensed Auckland plumbers for all of your plumbing, drain laying, gas-fitting and heating needs. Give us a call to see how we can help.