You turn on a faucet, and seconds later you hear it: a loud banging or knocking sound in pipes inside your walls. It might be a single startling thump or rapid-fire bangs. This alarming noise is water hammer. Learning how to stop water hammer protects your plumbing from serious damage.
While it sounds like your house is haunted, water hammer is a real physical event. It’s not just annoying—it signals a powerful shock wave straining your plumbing system. Over time, this can loosen fittings, damage connections, and even burst pipes.
At Repipe Solutions Inc., we know strange plumbing noises cause concern. This guide explains what water hammer is, its causes, and water hammer solutions that silence banging pipes.
What is Water Hammer?
Water hammer, or hydraulic shock, occurs when water flow suddenly stops or changes direction. Water has mass and momentum. When it flows quickly through a pipe and a valve suddenly closes, the water slams into the closed valve.
This creates a powerful shock wave that travels back through the pipe. The shock wave causes pipes to vibrate and bang against wooden studs and joists. This creates the characteristic hammering sound you hear.
Top 3 Water Hammer Causes
1. High Water Pressure
High water pressure is one of the most common water hammer causes. Higher pressure means water moves faster through pipes. Faster water has more momentum, creating more powerful shock waves when it stops.
Residential water pressure should stay between 40 and 60 PSI (pounds per square inch). Pressure significantly above 60 PSI leads to many plumbing problems, including water hammer in pipes.
How to check it: Buy a simple water pressure gauge that screws onto an outdoor hose bib. It gives an instant reading of your home’s pressure.
The water hammer fix: If pressure is too high, a plumber installs or adjusts a pressure reducing valve (PRV) on your main water line.
2. Failed or Missing Water Hammer Arrestors
Plumbing systems include features designed to absorb shock and prevent banging pipes.
Air Chambers: Older homes often have vertical pipe sections near fixtures. These “air chambers” contain air that cushions shock waves. Over time, they become waterlogged and lose effectiveness.
Water Hammer Arrestor: Modern plumbing codes require mechanical water hammer arrestors. These sealed devices contain a piston or diaphragm with compressed air. They install near fixtures and last much longer than air chambers.
If your home lacks these devices or existing ones have failed, nothing absorbs the hydraulic shock.
The water hammer fix: A plumber installs modern water hammer arrestors near problem fixtures. Washing machines, dishwashers, and fast-closing faucets typically need them most. Draining your plumbing system can temporarily restore air to waterlogged chambers.
3. Loose or Unsecured Pipes
Poorly secured pipes make water hammer much worse. Copper or PEX pipes not tightly strapped down vibrate freely. Shock waves cause them to physically bang against wall studs or floor joists.
The water hammer fix: This repair requires accessing pipes inside walls. A plumber may need to open drywall sections to secure loose pipes with new straps or clamps.
How to Stop Water Hammer: Step by Step
If you’re experiencing banging pipes, take these steps:
- Check your water pressure. If it’s above 60 PSI, call a plumber to install a pressure reducing valve.
- Try draining your system. Turn off your main water supply. Open all faucets at the highest and lowest points to completely drain pipes. This may temporarily restore air in old air chambers.
- Install water hammer arrestors. This is the most effective permanent solution. Install them as close as possible to problem fixtures.
Don’t Let Water Hammer Damage Your Plumbing
That knocking sound in pipes is more than a nuisance. It signals your plumbing system is under stress. Over time, this leads to serious leaks and water damage.
If you’re tired of banging pipes, contact the experts at Repipe Solutions Inc. We diagnose your water hammer causes—whether high pressure, missing arrestors, or loose pipes. We provide lasting water hammer solutions to silence the noise and protect your plumbing.
Call us today for a professional evaluation!