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Why Do I Hear My Plumbing Pipes Knocking When Hot Water Is On?

how water coming out of tap causing pipe banging noise
Plumbing repairs and maintenance are unavoidable in modern homes. Still, the situation can get downright terrifying if you don’t know what’s going on with your pipes.
Sometimes, strange noises emanating from inside the wall can startle you, especially pipes knocking while your hot water is on. A loud bang can be so unnerving that it can make you think there’s been an accident somewhere nearby (which could lead to more panic).

Your home’s pipes could be making loud knocking noises due to the following common causes:

  • Hot water pipes expanding and contracting
  • Loose pipes vibrating as water is running
  • Water hammering (high-pressure surges that move through a plumbing system)
In this blog post, we examine the causes of pipes knocking when you have turned hot water on, along with other scenarios, and look at how to fix the problems.

The Causes of Knocking Sounds in Plumbing Pipes (Including Pipes Knocking When Hot Water Is Turned On)

If you hear your pipes making strange, loud, or vibrating noises, there are a few possible causes.

Pipes Knocking When Hot Water Is Turned On

Poor CPVC piping may be the cause of constant loud and knocking sounds in your water pipes whenever a hot tap is on. The material of these pipes tends to expand and contract with heat, which can cause intermittent knocking sounds in the walls of different rooms within your home.
It’s important to know that some houses use CPVC piping as their supply pipes for hot water. If you hear knocking or banging sounds when running a shower, your problem could be coming from the bad construction of these lines.
Additionally, suppose this occurs in tight spaces where the sound resonates. In that case, it means improper installation work has occurred, including not putting down enough insulation around the pipes.
Otherwise, good quality PVC or CPVC should never cause issues while handling high pressures like those found inside homes without proper protection.
If you are experiencing unusual noises coming from your pipes, the only solution is to find their source and give the pipes more space to breathe. You could also opt to install copper plumbing for your hot water supply system instead of CPVC piping.
Installing new pipes can involve cutting into walls or relocating CPVC piping. We recommend hiring a professional plumber to do this job.

Pipes Making Loud Knocking Sounds When Cold Water Is Running

The noise you’re hearing when the water is running with a cold tap on could be because of high pressure. High pressure occurs when sections of pipe are not tight enough to handle the pressure well.
High-flow rates can produce turbulent flows, which shake and rattle along as they try to keep up with the fast-moving water around them. This phenomenon ends up causing those annoying loud bangs and knocks.
When you have a pressure issue in your home, it’s important to start by checking the incoming water supply. Install an adjustable pressure gauge on either side of every faucet and sewer drain near the mainline.
If any reading exceeds 80 PSI for more than ten minutes at a time without resolving itself within two hours, then call our plumbing professionals at MT Drains & Plumbing right away for assistance.

Pipes Knocking After Turning Off Hot or Cold Water

The most likely cause of loud knocking sounds in your pipes is a water hammer. This condition usually manifests as noises from the bathroom pipes when flushing a toilet or unusual knocks while running water from an appliance such as a water heater, dishwasher, or washing machine.
If this has happened recently, call in our professional plumbing team to check for leaks around the fixtures and other points where there is weakness. A weakness allows air into the plumbing system, causing a high-pressure surge that interferes with water flow. Such things can cause serious damage over time.
For more information on pipes making noise after turning off hot or cold water CLICK HERE.

Pipes Making Intermittent Loud Banging Noises When All Taps Are Off

We’ve looked at the causes of pipes knocking when hot water as well as cold water are on. But how about when all the faucets are turned off?
The most likely reason for such loud morning or evening noises is sediment buildup in the water heater. These sounds may be so annoying that you can’t help but wonder if there’s something wrong with your pipes.
Usually, the sound you hear is steam bubbles coming out of your water heater due to excess sediment buildup. This sound is similar to the sound made when covered boiling water in a pot pushes up and out as the pot’s base fills with residue and sediment.
Water heater tank heating elements sit at the base of the unit. This component is what heats your water for bathing, washing dishes, and other domestic chores. If a plumbing professional does not flush your water heater often, sediments can settle and mix with heated water.
The sediment that collects at the bottom of water heaters can turn hard between flushes because it has been there for so long. By calling in one of our expert plumbers to look into the problem, you can be sure that we will fix everything without costing you too much money or time.

Call in Our Expert Plumbing Team From MT Drains & Plumbing to Help You Fix Faulty Pipes

When you need a reliable and trustworthy plumbing service to help you fix knocking or leaking pipes, look no further than MT Drains & Plumbing. We serve Vaughan and the GTA in Ontario.
Our team has the skills needed to get any job done right—from regular plumbing maintenance services like installing new water heaters on old properties up to emergency repairs such as replacing burst pipes. Make us your go-to local professional plumbing service in Vaughan, Richmond Hill, Thornhill, Oshawa, and surrounding areas.
We guarantee prompt service, honest and reliable advice, quality workmanship, and upfront pricing for your total peace of mind.
If you are experiencing pipes knocking when you turn hot or cold water on, contact our expert plumbing team at MT Drains & Plumbing. Call us today at (905) 761-5551 to inspect your noisy pipes in Vaughan, Ontario.

Paul S

Paul has more then 20 years in basement waterproofing and plumbing projects experience. Looking for an advice from an expert plumber? Make sure to read Paul's articles about residential waterproofing and plumbing projects in Toronto.

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