How To Quiet Your Noisy, Knocking Water Pipes

Do you hear a knocking noise every time someone flushes the toilet, takes a shower or uses a faucet?

Besides being a nuisance, the problems causing this noise can hurt your plumbing and shorten the lifespan of your fixtures.

There are 3 possible causes of a knocking noise. For each one, we’ll show you:

• What it is
• How to tell if it’s the source of your knocking noise
• How to fix it

Loose supply pipes knocking against a wall

What it is: Over time, the pipes that supply your fixtures with hot and cold water can work loose from their straps (often from water hammer. See below.) Then the high water pressure that passes through the pipes causes them to knock against the wall that they’re supposed to be secured to.

This noise can be especially pronounced if you have masonry walls (brick, concrete block, etc.).

How to tell if this is your problem: This noise will happen only when water is running. As soon as you turn off the faucet or shower, the noise should stop.

How to fix it: If you can get to the loose pipes, tightening or installing straps so that the pipes are secured will eliminate the problem. Keep in mind that you don’t want to anchor the pipe so tightly that it can’t expand and contract with changes in temperature.

A pipe strap securing a pipe to a wall.

If the loose pipes are in the walls, you may be able to eliminate the knocking noise by placing padding or foam insulation at each end where the pipe comes out of the wall.

High water pressure

What it is: Too much water pressure may cause your pipes to rattle around even if they are secured well.

How to tell if this is your problem: The knocking noise will likely be a quieter tapping rather than full on knocking. And it will only occur when the water is running. If it only happens when you run hot water, only your hot water pressure is too high.

How to fix it: Normal water pressure is 40-80 psi. Anything above that and you might experience some knocking noises. If your cold water pressure is above that, consider adjusting (or installing) a pressure reducing valve (PRV).

Check out this video on checking and adjusting your water pressure or contact a plumber for help with this.

If the problem is with your hot water, try turning down the temperature a bit to see if that helps. You can also install a water heater expansion tank. Heating water causes expansion, which increases water pressure. A water heater expansion tank absorbs this increased pressure, keeping it out of your pipes and fixtures.

Water hammer

What it is: Water hammer is sometimes used to refer to any noise coming from your plumbing, but it’s a specific noise. It’s caused from a valve suddenly shutting and the water crashing into the valve and the water in front of it.

Think of it like a car stopping suddenly on the highway during rush hour. All the cars behind it would crash into it, causing quite the commotion.

How to tell this is your problem: You’ll notice a water hammer when you shut the water off. There will be no knocking noise while water is running.

How to fix it: Depends on the age of your home:

• Homes built prior to the 1960s—You likely have air chambers installed in your home that act as shock absorbers. However, over time the air can be displaced by water. You can fix this easily by shutting off the water to your home and opening all your faucets to drain all the water from your pipes. Then turn your water back on.
• Homes built since the 1960s—Homes are now built with water hammer arrestors, which are spring-loaded shock absorbers that don’t fail often. If you are experiencing a water hammer, your home may not have been installed with these arrestors. You’ll need a plumber to install them for you.

Get a professional Atlanta plumber’s help

Want to get rid of that knocking sound for good? Enlist the help of a licensed plumber like Mr. Plumber. We serve the entire Atlanta metro area including Marietta, Lawrenceville, Woodstock, Alpharetta, Douglasville, Newnan, Peachtree City and more. Contact us today.