Reasons Why Your Plumbing Pipes Make a Knocking Noise

Hearing your pipes making a knocking noise can be spooky, and worrisome. You’re probably wondering why that could be happening. After all, it seems more supernatural than natural. Thankfully, there are real-world reasons this is happening. Here are some reasons why.

Reasons Why Your Plumbing Pipes Make a Knocking Noise

Loose Pipes

Over the years, the hot and cold supply pipes in your home can become loose. The straps that hold them in place can deteriorate. When water runs through pipes that are loosened, the pressure can make them bounce against the wall. If you only hear the pipes knocking when water is running, it’s a good indication that loose pipes are the culprit.

If you can reach the offending pipes, you can secure them. If you do this, make sure not to secure them too tightly, as the pipes will need room to expand and contract, depending on water pressure. If the pipes are inside the wall, you may be able to prevent the knocking noise by stuffing padding or foam at each end of where the pipes go into the wall.

High Pressure

If the water pressure in your pipes is too high, the pipes will knock around, no matter how securely they’re fastened to the house. Like loose pipes, you’ll only notice this when the water is running. With high-pressure issues, it’ll be less of a loud knocking sound, and more of a quiet tapping sound. Water pressure in your pipes should be between 40 and 80 pounds per square inch. If your cold water is running higher than that, you may want to consider installing a pressure reduction valve. If it’s the hot water, try turning the temperature down on the hot water heater, or installing a hot water heater expansion tank to reduce the pressure.

Water Hammer

A loud knocking sound that occurs only when the water is turned off is usually a sign of a water hammer issue. Water hammer is caused by a valve suddenly shutting off, causing the water in the pipes to slam into it. Older homes come with air chambers installed that can become filled with water. Shutting off the main water supply, and running all the faucets in your home will drain the pipes, and fix the water hammer. For newer homes, water hammer arrestors are installed, which act as shock absorbers in the system, and prevent water hammer. If they’re failing, a licensed plumber can fix the issue.

If you have questions or concerns about the knocking in your pipes, don’t hesitate to call the expert team at Emergency Plumbing & Solar. We’re here for you 24/7 at (808) 691-9309.


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