How to Fix Water Hammer in Pipes (2024)

Water hammer is acommon plumbingproblem. It creates an annoying sound, a loud knock, or repetitive banging that can be quite startling. And while you may want to wish it away as simply one of those harmless everyday sounds, it can damage yourplumbingsystem. Learning the basics of water hammer and fixing it can save you thousands of dollars in repairs.

What Is Water Hammer?

Water hammer is the sudden stoppage of water flow that causes water supply pipes to bang against studs, joists, beams, or even against other water supply or drain pipes. Also called hydraulic shock, it causes an alarming sound and a sensation. It can sound like a repetitive hammering sound from the walls, and you can often hear vibrations from the pipes or house supports near it.

It's often strong enough to feel it under your hand as you hold the faucet or the handle. You may even see the faucet slightly jump. The shock waves from the water hammer can even cause dishes and glasses in cabinets to vibrate.

What Causes Water Hammer

Water hammer is caused by water being shut off quickly in plumbing systems with blocked or non-functioning air chambers. In properly running plumbing pipes, these air chambers prevent the water from stopping suddenly and banging against the studs, beams, or other pipes. When these pipes hit together, they can loosen the pipes from their fittings, causing them to burst or come undone suddenly.

While sink, tub, and shower faucets can cause water hammer, clothes washers and dishwashers can more often cause water hammerbecause they can shut off water faster than by hand. These appliances usesolenoid valves, which can close off as quickly as 30 milliseconds.

How Water Hammer Can Damage Plumbing

Left untreated, water hammer can cause significant damage by destroying pipework, the home's plumbing system, and appliances connected to the pipes. This damage has a ripple effect that can result in water damaging the home, mold issues, and structural integrity issues like rot.

• Water leaks
• Ruptured pipes
• Plumbing joint failure
  
• Damage to pumps and valves
• Appliance problems
• Exterior and structural damage

Methods for Fixing Water Hammer

Air Chambers

Air chambers can quiet water hammer by acting as a shock absorber for the water that comes to a sudden halt. Air chambers look like capped pipes extending from the supply pipes. The air chamber acts as a cushion for the water, compressing the air in the chamber and not putting pressure on the rest of the pipework.

This simple solution requires advanced plumbing skills for installation. Plus, air chambers can fill with water over time, so the pipes may occasionally need to bedrained.

Water Hammer Arresters

Awater hammer arresteris a simple device installed on a specific fixture or appliance. Arresters absorb the shock wave created by a sudden stoppage of the water flow.It is similar to an air chamber; the main difference is it has a chamber filled with gas or air that's sealed with a piston or diaphragm. The diaphragm separates the water and the gas or air.

Awater hammer arresteris often spliced into the point where the water supply hose meets theshutoff valve. No pipes need to be cut or sweated back together. Look for water arresters that are combined with a valve.

Water-Pressure Regulators

A water-pressure regulator ensures that the overall water pressure from the main line entering the home remains at a safe level. Normal water pressure runs between 40 and 60 psi (pounds per square inch); above this, high water pressure can cause water hammer. Water pressure above 80 psi can also damage appliances.

Install the water-pressure regulator where the main water supply enters the home. Putting the device at the main water supply protects dishwashers, toilets, and other appliances and fixtures against high water pressure. If you suspect you're having water pressure issues, test the water pressure. You can get an inexpensive water pressure gauge from most hardware stores.