What Exactly Causes Water Hammer?

Tap water

The term ‘water hammer’ refers to banging noises that sometimes come from plumbing pipework. It’s usually one, or a series of banging noises coming from the pipework and you will find it usually happens when a tap or valve is turned off.

It is often caused by high pressure water systems either when a tap is turned off quickly, or by fast acting valves on appliances that stop the water from moving through the pipes suddenly, causing the pipes to ‘shudder’. Water hammer can be made worse by having worn valves and pipework that is not supported properly. Here we’ll talk more about water hammer, what will happen if you don’t fix it, and how you can remedy it.

It’s more than just a funny noise!

What Are The Causes Of Water Hammer?

There are a number of things that could be causing water hammer.

If the water hammer only started once work had been completed on the plumbing system or you had a new appliance installed, then you should take a look at those areas to find the cause.

However, any change to a plumbing system might start water hammer in another area.

Water hammer diagram

The possible causes of water hammer include:

  1. Worn stop valves
  2. Ball and float valves
  3. Washing machines and dishwashers
  4. Inadequately secured pipework

If you only hear water hammer every so often, then you likely don’t have a serious issue.

Water pressure can sometimes spike in residential plumbing because of an issue with the water supply.

However, if you hear it regularly, it could threaten the safety of your pipes and your home.

High pressures inside of your pipes can damage them, and later result in burst pipes.

So, how can you fix the issue?

Install An Air Chamber

For an expert plumber this is fairly simple to do; simply install a short segment of vertical pipe near the valves that are causing the water hammer.

This method creates a segment of empty, air filled pipe that provides a cushion for water to rebound into it when it attempts to change direction suddenly.

The only issue with this method is that it can become filled with water and stop functioning correctly.

Air chamber diagram

You can correct this by periodically draining the entire water supply system, which will restore air to the chambers.

Air chambers can also become clogged with debris on rare occasions.

They can be cleaned by removing the caps and scouring them out.

Installing air chambers that are larger in diameter than the main plumbing lines can also help prevent clogging.

Install A Water Pressure Regulator

Water hammer also occurs when the overall pressure of the main water pipe entering the building is too high.

Normal water pressure runs between 30 and 55 psi (pounds per square inch), and if it is above this it could be causing the water hammer.

Very high pressure will damage your appliances – this is anything over 100 psi.

Water pressure regulator

A water pressure regulator can solve these issues.

It’s better to install a regulator at the location where the main water supply enters the home instead of installing multiple air chambers, because this will also protect your toilets, dishwashers, and any other appliances from high water pressure.

You should test the water pressure first so you can be sure that it’s higher than it should be.

Once you have installed the water pressure regulator at the main water supply entry, you can adjust the regulator to a pressure that is below 50 psi.

Secure Your Loose Pipes

Even a mild tremor can create a loud banging noise if your pipes are not well secured.

A mild case likely won’t cause long term pipe damage, but you can prevent anything like that from happening in the first place by tightening loose pipe straps of hangers that secure the pipes to studs or joists.

Plumbing pipes

Segments of foam pipe insulation wrapped around the pipes can act as shock absorbers and prevent banging, too.

Installing Mechanical Water Shock Arrestors

Mechanical water shock arrestors are a more sophisticated form of absorbing the shock from water hammer than other methods, and they’re good to use in situations where an air chamber simply isn’t practical.

Water shock arrestor

They are often used in commercial buildings and for high water pressure applications.

Mechanical water arrestors do not need to be recharged like air chambers, but they will need to be replaced when the inner springs and bladders wear out.

They have a life cycle so it’s important to make a note of this so that you are prepared.

Final thoughts

Water hammer can be a serious issue if it’s happening very frequently, because it can signal a warning that your pipes are under heavy stress and at risk of bursting.

So if you don’t want to risk thousands of dollars in repair work because of a burst pipe, have a licensed plumber come and fix it, before it turns into a major problem.

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