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Fixing Knocking & Banging Pipes


Plumbing systems are generally not silent because of what’s involved – large volumes of water traveling at high-speeds through metal or plastic pipes. But when your pipes are banging, it can quickly become a nuisance. The first thing to do is identify when pipework gets noisy.

Do you hear a banging noise after you turn on the tap?

A clunking noise or knocking noise followed by a drop in the flow of water usually means some material has broken off the tap or the valve and is blocking the pipe. You’ll need to open the tap and valve to clean out the debris.

Does the knocking noise start only while the hot water is running?

You can blame poor construction of CPVC water lines. CPVC piping naturally expands when hot water runs through it, so there should be plenty of free space around it to prevent friction. If it’s lodged in a tight area, you’ll hear the banging noise.

 Does the knocking sound from the pipes start while cold water is running?

If the water pressure is higher than normal, the force of the water against the pipes generates the rattling sound. A professional can do a simple water pressure test to see if you have high water pressure.

 Do you have hanging pipes from your ceilings or walls?

Loose pipes are the most common culprit. To make them a lot quieter, you’ll need to securely fix water pipes with high-quality pipe clips using the right equipment. A plumber can help you decide what equipment is the best for your home.

 Do you hear random banging noises even when there’s no water running?

The most likely cause is sediment build-up in your water heater. The heating element for your water is located at the bottom of the tank, so the loud bang is produced once enough steam bubbles pass through the sediment layer.  A professional plumber can flush your water heater or you can do it yourself.

If the knocking happens after a cold or hot water supply shuts off, when a toilet flushes, when the clothes washer finishes filling up or when your home’s sprinkler system turns off, you have a water hammer. This phenomenon can be violent enough to shake the pipes loose of their joints and cause massive leaking. Fixing the water hammer depends on when your home was built.

Homes built before the 1960’s: the pipework is frequently constructed with air chambers, a pipe with a “T” fitting capped off at the top, to prevent water hammer. When the air chamber is functioning properly it becomes filled with more water than air. 

Homes Built between 1970-1990’s: these homes have little to no water hammer protection. If you hear loud banging noises, contact a professional plumber to have water hammer arresters installed.

Homes built after 2000 - present: Luckily, modern homes are built with water hammer arresters that never become water logged. If you’re experiencing a water hammer then one or more of your water hammer arrestors may have malfunctioned or they were never installed.

Overall, noisy pipes are trying to tell you something. If you listen closely, you’ll hear what’s wrong. Contact the Superior Drainage experts today for help with your banging pipes.