Skip navigation

Estimates are free!

24 hour Emergency Service


Northwest Vermont & Northeast New York


Why Am I Hearing a Knocking Sound from My Water Pipes?

Unexpected noises from any part of your house can be alarming, and often something that you should investigate. A rumbling water heater tank, rattling from a furnace, or clanging from an air conditioner are all examples of appliances that may be malfunctioning.

Your freshwater plumbing can make its own warning sound: a sharp knocking noise. What exactly does this mean, and does it call for professional repair services?

Water Hammer

This knocking noise that you’re hearing is called water hammer or hydraulic shock. It’s the result of shock waves inside the freshwater pipes. When the water in the pipes is forced to stop abruptly—usually at a closed tap—the sudden spike in pressure creates a distinctive knocking noise. You are most likely to hear water hammer after a major water-using appliance shuts off, such as a washing machine, dishwasher, or toilet.

Is This a Problem?

Most of the time, it is. Your freshwater plumbing system is designed to avoid these shock waves by using air traps and dampers to soften the force when water stops as a tap is closed off. If these air traps become water-logged or the dampers fail, the shock waves can cause damage to the plumbing. These vibrations can cause pipes to break.

What Can Be Done about It?

Professional plumbers are familiar with the effects of water hammer and the various methods necessary to protect freshwater pipes from it. In most cases, the plumbers will only need to restore the air traps to return the safety air cushion. They may also recommend shorter pipe lengths if your house has older plumbing, or look for other ways to reduce pressure in the pipes by attaching pressure-relieving valves on the incoming water supply. It’s important to leave this job to licensed plumbers, since an incorrectly attached valve can end up lowering water pressure throughout a house.

Red Rock Mechanical LLC serves the Plattsburg, NY area. Call us whenever you need plumbing repairs, installations, or other services.

Comments are closed.