# Pipes banging when you turn off the water: how to stop water hammer

Updated: 2026-10-24 · https://pros411.com/en/guides/plumbers/pipes-banging-water-hammer

## Short answer

That bang is water hammer: fast-moving water stops all at once when a valve closes. Check the pressure with a gauge on an outdoor faucet: above 80 psi, have a plumber adjust or install a pressure-reducing valve. Then drain the pipes to refill the air chambers, strap loose pipes you can reach and add water hammer arrestors on the washing machine valves.

## How to stop water hammer

![Cartoon pipe inside an open wall banging against a stud, next to a washing machine, with a startled cat](https://pros411.com/img/guias/pipes-banging-water-hammer.webp)

1. **The valve shuts and the pipe goes BANG.** Water rushing through the pipe stops all at once. The shock shakes the pipe and it knocks against the wood inside the wall.
2. **Check the water pressure.** Screw a pressure gauge onto an outdoor faucet or the washer valve and open it. Most homes run at 40 to 80 psi. Higher than that makes hammer worse.
3. **Drain the pipes so the air chambers refill.** Shut off the main, open the highest and the lowest faucets and let the water drain. Close them and turn the main back on: the air chambers fill with air again.
4. **Strap down loose pipes.** Where you can reach the pipes, in a basement or crawl space, add pipe straps with a rubber cushion so they cannot slam into the framing.
5. **Add a water hammer arrestor.** Screw-on arrestors fit between the washer valve and its hose. Hand tight, plus a quarter turn with pliers. Now the valve shuts quietly.

## Why it happens

- Fast-closing valves: washing machines, dishwashers, ice makers and single-handle faucets.
- High water pressure.
- Air chambers that filled with water over the years and stopped cushioning.
- Pipes that were never strapped down, or whose straps came loose.

## What not to do

- Do not ignore it: the repeated shock can loosen joints and cause leaks.
- Do not slam single-handle faucets shut: close them gently.
- Do not open a wall to chase the noise: a plumber can add an arrestor near the valve that causes it.

## Noises that are not water hammer

Ticking or creaking while hot water runs is the pipe expanding against the wood. Rattling while the water runs, not when it stops, is usually a loose pipe or a worn faucet washer. A buzz or chatter when a toilet refills often means a worn fill valve.

## When to call a plumber

- Your water pressure reads above 80 psi (a pressure-reducing valve needs adjusting or installing).
- The banging comes from pipes inside walls or ceilings you cannot reach.
- It started after plumbing work, or it keeps getting louder.
- You see drips or damp spots near the pipes that bang.

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## Frequently asked questions

### Why do my pipes bang when I turn off the water?

Water moving through the pipe stops suddenly when a valve closes, and the pressure wave makes the pipe jump and knock. Fast-closing valves and high pressure make it worse.

### Is water hammer dangerous?

Not right away, but it is hard on your plumbing. The repeated shock can loosen joints, wear out valves and appliances and lead to leaks over time.

### What is a water hammer arrestor?

A small capped cylinder with a cushion of air or gas inside that absorbs the shock. Screw-on versions fit washing machine valves; others are installed in the line by a plumber.

### What is normal water pressure for a house?

Most homes run between 40 and 80 psi. Above 80 psi, water hammer and leaks get more likely, and a pressure-reducing valve is usually needed.

### Why does the washing machine make my pipes bang?

Its fill valves are electric and slam shut in a split second. That is why arrestors at the washer valves fix most water hammer in the laundry room.

### Will draining the pipes fix water hammer?

Often, if your house has air chambers that filled with water. If the bang comes back within days, an arrestor is the better fix.