Do I Need Hammer Arrestors in My PEX Plumbing?

If you've ever dealt with water hammer, you're familiar with the loud, sudden banging it causes. While this effect is most prominent in copper pipes, other types of plumbing pipes, including PEX pipes, also experience water hammer. Installing water hammer arrestors designed for PEX can help reduce the effects.

Water moves through your plumbing with help from water pressure, but that pressure can also cause clanging and banging in the pipes. Water hammer happens when you're running water and shut it off. The sudden stop means the water pressure has nowhere to go, so it vibrates back through the pipes, much like a shock wave. You'll often notice it when your washing machine finishes filling, and the shutoff valve closes suddenly.

Certain situations can make water hammer more intense. If your home's water pressure is too high, it can increase the vibrations and cause louder banging. Large appliances that use water, such as dishwashers and washing machines, might make the vibrations worse.

You likely think of metal pipes when you think of a banging noise, but water hammer can happen in all types of pipes, including PEX plumbing. If left unaddressed, water hammer can cause leaking connections in your PEX plumbing.

Water hammer arrestors help dissipate the pressure with air-filled cylinders containing pistons. This air absorbs the pressure since air compresses (unlike water, which doesn't compress) to cushion the shock waves created by the water pressure. Reducing the pressure and vibrations helps protect your plumbing lines and connections. Water hammer arrestors don't need any maintenance and attach easily to the plumbing.

Cross-linked polyethylene (PEX) is flexible plastic used to create plumbing lines that can replace traditional metal water supply lines. It's common in new construction, and homeowners often switch to PEX when they remodel. PEX is color-coded, using red for hot water, blue for cold water, and white and gray for either hot or cold water.

The main benefit of PEX is its flexibility. Instead of having several shorter sections connected to go around turns and move through your home, you can use one long piece of PEX and bend it to maneuver it through different areas.

That flexibility and the softer construction mean a PEX line might not bang loudly when water hammer occurs. However, the shock wave still goes back through the plumbing and can cause damage, including loosened connections and leaks.

For new plumbing installations, local building codes might require water hammer arrestors on quick-closing valves, which would include things like washing machines and dishwashers. Check on your local building codes or with your plumbing contractor to determine whether you need them.

Even if they're not required for your PEX plumbing, you might decide to install them. You can find water hammer arrestors for PEX if you want to add them to your PEX plumbing. Sioux Chief and SharkBite are two brands that make PEX-compatible arrestors.