Knocking pipes (often called "water hammer") are not usually an immediate emergency, but you shouldn't ignore them. If left unaddressed, the shockwaves can loosen joints, rupture pipes, and cause leaks. The specific cause determines how concerned you should be:
Hearing your pipes knock when turning on or off the water is a common plumbing issue that can stem from a variety of causes, most of which relate to pressure changes, loose components, or disruptions in water flow within your plumbing system. It can be a mere nuisance or a more serious plumbing problem.
However, the loud bang or series of bangs or shuddering noises is normally more of a shock to a homeowner than the plumbing system. Don't panic. The sound is unlikely to damage your pipes and there is a relatively easy fix.
Water hammer is a loud banging or rattling noise in your plumbing system caused by water suddenly stopping and violently slamming against the pipe. You can easily stop it by installing water hammer arrestors near the problem appliances, securing loose pipes with foam insulation, or recharging the air in your plumbing lines.
Air in the Pipes
Air trapped inside your plumbing system can also cause pipes to knock. This usually happens when water is being drained from your system or if there is an issue with your plumbing's air chamber. Air pockets can create a knocking sound as water passes through the pipes, even when no faucets are on.
To diagnose and fix water hammer in a cold water system, check for air pockets or loose faucet washers, and consider installing a water hammer arrestor or expansion tank. "That's water hammer. Call a plumber (unless you're comfortable doing plumbing) you need a water hammer arrestor."
Here's how you can prevent your pipes from bursting after shutting off your water: Insulate your pipes: Make sure all exposed pipes are sufficiently insulated, particularly those located in cold spots throughout your home, like attics and basements.
How long will water hammer last? Although the banging noise you hear from water hammer may only last a few seconds, the issue within your pipes will last until you take steps to fix it.
This can be fixed by draining your plumbing system, which requires turning off the main water valve and opening the highest faucet in your home. Then drain water from the lowest faucet. The chamber should fill up with air once the water is drained and resolve your water hammer problem.
Consequences of Ignoring Water Hammer
Repeated pressure waves put stress on joints, fittings, and pipe supports, loosening them over time and significantly increasing the risk of leaks. In severe instances, these pressure surges can even cause pipes to burst, potentially flooding rooms and damaging flooring or walls.
PMRs for malignancies of the stomach, kidney, brain, and lymphopoietic system were also elevated, especially among plumbers. Chronic rheumatic heart disease, emphysema, liver cirrhosis, and all external causes of death were the major non-cancer causes with significantly elevated PMRs.
The 135 rule means horizontal drain pipes cannot connect using a fitting that creates more than a 135-degree change in direction. In plain terms, you cannot use a standard short-turn 90-degree elbow between two horizontal drain lines. Plumbers use two 45-degree elbows, a long-sweep 90, or a wye-and-eighth-bend instead.
Damage to Pipes: Repeated high-pressure shocks can weaken the walls of the pipes, leading to leaks, cracks, or even bursts. In severe cases, the entire pipeline could fail. Pump and Flow System Damage: Water hammer can cause significant damage to pumps, valves, and other components in the flow system.
Water hammer has a number of potential causes, all of which have been detailed below.
WATER HAMMER: A loud bang in your pipes after a fill valve shuts off. Water hammer can be caused by worn or damaged faucet washers. Also, heavy build-up of minerals and rust inside shut off valves (located on the walls of your home) can cause water hammer.
Yes, water hammer is a common plumbing issue that affects both residential and commercial properties. The problem can occur with any plumbing fixture that requires quick shutoff, such as washing machines, dishwashers, or even standard faucets.
Installing a water hammer arrestor can be complex and costly if done incorrectly, so it's best to hire a plumbing professional to ensure the job is done correctly the first time.
Piping systems without bends or loops: Systems that feature long lengths of pipe without directional variation can result in excessive fluid velocity, which worsens the effects of water hammer when it's inevitably caused by a closing valve.
💷 Main costs to expect
Labour: Typically one to two hours, charged at around £40–£60 per hour for a qualified plumber. Materials/parts: Water hammer arrestors usually cost between £20 and £60 each depending on size and type. Extras: If pipework needs adapting or new valves fitting, this might add £30–£80.
Water hammer isn't an emergency, but it is something to be concerned about in the sense that you want to have it addressed by a professional ASAP.
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To know if a pipe has burst, watch for a sudden drop in water pressure, sputtering faucets, and water sounds (like dripping or hissing) when no taps are on. Visually inspect for wet or warped drywall, peeling paint, discolored water, or unexplained wet spots on your lawn.
While it may be tempting to save a few bucks on your heating bill at times, a cold snap is not the time to set back the thermostat if you have pipes that are at risk of freezing. Leave the heat on if you plan to be away during cold weather. Set the thermostat to a temperature no lower than 55° F.
In conclusion, while a pipe leak can stop on its own, it's not a permanent fix. It's important to address the underlying issue and take steps to prevent further damage.
When a cold snap hovers around or below 32 degrees Fahrenheit for a couple days in a row it's time to let at least one faucet drip. Pay close attention to water pipes that are in attics, garages, basements or crawl spaces because temperatures in these unheated interior spaces usually mimic outdoor temperatures.