Water Hammer Explained: Why Your Pipes Bang

w to Fix Water Hammer in Your Home

Quick Summary
Water hammer is a shockwave caused by fast-moving water that suddenly comes to a stop in your pipes. The rapid stop is usually caused by fast-closing valves on your washing machine, dishwasher, and refrigerator ice maker. Over time, water hammer can loosen fittings, damage valves, and even cause leaks behind walls. The most effective ways to fix it are to reduce high water pressure, secure loose pipes, and install mechanical water hammer arrestors—especially at appliances like washing machines.

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What Is Water Hammer? (And Why That Bang Isn’t Harmless)

Water hammer occurs when flowing water suddenly stops—usually because an electrically controlled solenoid valve snaps shut. When that happens, the moving column of water has nowhere to go. Water doesn’t compress. So instead of slowing down gently, it slams against the closed valve and sends a shockwave backward through your plumbing system. The shockwave can be powerful enough to shake pipes inside your walls.

This is especially common in washing machines, dishwashers, and refrigerator ice makers when a cycle changes. The solenoid valve shuts off instantly, and boom—you get that unmistakable bang. However, it can also occur in some toilet fill valves, where the float rises slowly until the end of travel and then shuts off abruptly.

High water pressure is one of the biggest contributors. In some areas, incoming pressure exceeds 100 PSI. Even in moderate-pressure areas, I’ve seen homes sitting at 70–80 PSI without a pressure-reducing valve. That’s plenty to create serious water hammer.

Why You Should Never Ignore It

Every time water hammer happens, you’re stressing your plumbing system. Over time, that shockwave can:

• Loosen threaded fittings
• Crack poorly soldered joints
• Damage appliance valves
• Split weak copper lines
• Cause hidden leaks behind drywall

How I Fix Water Hammer the Right Way

1) Check the water pressure. You can buy a water pressure gauge at most home center stores. This one is

Water pressure test gauge

from Home Depot and costs just $10.50. Simply screw it onto the garden hose threads on your laundry tub faucet or the water valve to your washing machine. Then open the valve and read the result.

If it’s over 75 PSI, I recommend installing or adjusting a pressure-reducing valve. Lowering system pressure can dramatically reduce water hammer.

2) Second, I inspect pipe supports. Loose pipes amplify the banging sound. Securing and strapping pipes properly can help fix water hammer without any specialty devices.

The Most Effective Way to Fix Water Hammer is at the Source

That’s where mechanical water hammer arrestors come in. These small, pre-charged devices install directly between the valve and the washing machine, dishwasher, or ice maker. They contain an internal air chamber separated by a piston or diaphragm. When shutoff occurs, the shockwave is absorbed into that chamber instead of slamming into your pipes.

Different types of water hammer arresters

Installation is straightforward:

Remove your existing hoses from the back of the washer and install the arrester. For a dishwasher, shut off the water supply valve under your sink, and disconnect the dishwasher supply hose. Then install the arrester onto the supply valve.

Common Question: Do Water Hammer Arrestors Need to Be Upright?

No. Modern mechanical arrestors don’t rely on a simple air pocket like old-fashioned vertical standpipes did. They’re sealed units and can be installed horizontally or vertically.

That’s important in tight laundry spaces or stackable washer/dryer setups.

The Long-Term Risk of Ignoring Water Hammer

If your plumbing system is old, and you keep allowing repeated water hammer, you are gambling with leaks. Eventually, something gives.

I’ve seen ceiling collapses from burst fittings, and washing machine valves split. I’ve also seen copper lines develop pinhole leaks from years of shock stress.

If you want peace of mind, fix water hammer before it becomes a repair emergency.

©, 2026 Rick Muscoplat