What’s Water Hammer and how do I fix it?

Water hammer diagram demonstrating the phenomenon of water hammer.

Even if you don’t know what water hammer is you’ll probably have experienced it at some point in your life.

In short it is a noise which sounds very much like hammering and it comes from your pipes. The noise is usually heard when you turn off a faucet. When you do this you’re preventing the water from exiting your pipes and effectively turning it back on itself. This creates a wave inside your pipes which translates as a hammering noise.

If you already have high water pressure then water hammer can cause serious damage to your pipes and fittings. The pressure inside your system can actually cause joints to break apart or washers to fail; leaving you with a leak that needs prompt attention.

That’s why it is important to deal with water hammer as quickly as possible. Fortunately there are several things you can do to resolve the issue.

The Air chamber

An air chamber is simply a vertical piece of pipe which you install next to the valves; especially near where you’re hearing the hammering sounds. The vertical pipe creates an air chamber which buffers the water preventing the waves from happening.

In effect they absorb the pressure differences in your water erasing the problem.

Water Pressure

The higher your water pressure the greater the hammer effect. This is simple physics. When you shut off the valve the greater the pressure behind it the more water there will be to turn back on itself. Therefore the louder or longer the hammering will go on for.

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By reducing the water pressure you can eliminate the issue. This doesn’t mean half closing a valve somewhere in your system. You’ll need to install a water pressure regulator near where the water supply comes into your house.


An alternative way to reduce your water pressure and improve the flow of water to specific appliances is to use a pump; similar to ones used in mine dewatering systems.

These will absorb pressure differences and prevent water from flowing back on itself; effectively eliminating any water hammer and protecting your plumbing.

Of course a good pump can also increase the water pressure. This makes it a great choice to work with your pressure regulator and still having a high powered shower.

Mechanical Valves or Arrestors

These are an effective alternative when it’s not possible to fit air chambers. These small units slot into your plumbing system near the location of your hammering. They are sealed with an air bladder and spring inside them.

These two items work in the same way as an air chamber to absorb differences in water pressure and reduce or eliminate the water hammer effect.

It’s worth noting that while an air chamber needs to be periodically recharged the mechanical arrestor won’t. But, it will need to be replaced according to the manufacturer’s guidelines.

Whichever course of action you choose to take it is essential that you do something about your water hammer today. The longer you leave it the more likely it is that you’ll have a bigger problem to deal with.

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