How to stop a hot water heater from knocking?

Author: Linda Koelpin  |  Last update: Sunday, July 12, 2026

Does your water heater make a knocking/rumbling noise that could wake the dead? If so, your water heater tank has most likely collected a thick layer of sediment (minerals like calcium and lime). The solution: Drain the water heater tank and flush out the sediment.

How do I stop my water heater from water hammering?

Water hammer can usually be solved by adding an expansion tank to the water heater, and water hammer arrestors at strategic locations. Most municipalities now require backflow preventers (check valves). Before this, the entire city water supply acted as a kind of expansion tank. They can help alleviate hammer.

Why is my hot water heater making a tapping noise?

This knocking noise is likely due to mineral deposits, or sediment, that has gathered at the bottom of the tank--also known as scale. The sound is due to the reduced volume in the tank, which forces steam bubbles to rise as the burners heat the tank.

How do I stop my hot water pipes from knocking?

There are three steps to take: 1. make sure the pipes are securely mounted; you can add a rubber insulator between pipe and bracket. 2. Lower the water pressure, though this seldom works as the problem is the waters momentum/velocity not it's pressure. 3. Install Water hammer valves in the line.

What is the hammering sound on my water heater?

Popping Noise: A popping sound usually means there is sediment buildup inside the tank, likely from hard water or rust. Knocking/Hammering: A hammering sound could be from sediment buildup or something called water hammer, which is caused by water flooding back through your pipes after water is turned off.

What to Do About Water Heater Knocking Sound | Percolating Water Heater Sound

How to fix a water heater knocking?

Flushing Water Heaters

Start and stop your cold water valve, eliminating excess scale. Next, disconnect your hose, close your drain valve, and shut off your faucet. Lastly, fill up your tank and ensure no warm air bubbles are present. Then, turn the water heater back on according to your manufacturer's guidelines.

Why does my heater make a knocking sound?

Dirty Blower Wheel

Regular maintenance always benefits your furnace, and this definitely applies in the case of the blower wheel in your furnace. If the blower wheel becomes unbalanced, you may hear knocking sounds when the furnace runs.

Why is my hot water system making a knocking sound?

While it's normal for a hot water heater to make a slight knocking sound due to the natural expansion and contraction of the metal tank during the heating process, excessive knocking likely results from a bigger problem such as loose parts, corrosion, or sediment buildup.

Is a water hammer bad for pipes?

Leaks: Water hammer has the potential to damage joints, fittings and connections, resulting in poor seals and ultimately leaky pipes. Ruptured pipes: Ruptured pipes due to built-up pressure can be particularly expensive to repair. Due to the nature of the repair, it will often entail a major replacement operation.

Is it bad if your pipes are knocking?

The flow of water through the loose pipes can cause them to hit their walls and it's like a noise you get when you knock. Problems happen only if the water runs, and if the banging noise stops when shutting down water, it's a good indication there's a leakage.

How to stop a water heater from making noise?

A water heater making humming noise is probably caused by a loose heating element. The loose element makes the water around it vibrate, creating a humming sound. Tightening the element should eliminate the hum.

How often should I flush my water heater?

Most homeowners should flush their water heaters every 6 months or so, but if you have extremely hard water, you may want to do it more often. Flushing your hot water heater could be necessary as often as every few months depending on the mineral content of your local water supply.

Can a hot water heater cause water hammer?

If water hammer is occurring in your home, it could be due to a variety of things. Your water heater could be overfired, which means the burner is causing the water to heat up too quickly, turn to steam, and get jetted throughout your pipe system causing things to knock around and contract rapidly.

Can I fix a water hammer myself?

You can fix the problem by tightening the screws holding loose pipe straps. Additional straps can be added to improve stability. Pipe straps are usually made of thin metal or plastic, while padded types are available to reduce vibration.

How to get rid of air in water pipes?

Remove air from your pipes in five easy steps:
  1. Turn Off Your Main Water Supply Valve. ...
  2. Open all the faucets in your house. ...
  3. Wait for All Faucets to Run Dry and Flush Toilets. ...
  4. Turn the Main Water Supply Back On. ...
  5. Turn All Faucets Off Again in the Correct Order.

Why does my forced hot water heating system make a banging sound?

Air Trapped in System

When air gets trapped in what is supposed to be a sealed heating system, the bubbles in the water can cause rattling, clanging, and banging noises. This requires a process known as bleeding to remove the air from the system. It's best handled by an HVAC technician.

Do I need a plumber for water hammer?

A water hammer is a surefire sign that damage may occur in your plumbing pipes. Therefore, you should enlist a plumber to inspect the plumbing system should you hear of any water hammer before permanent and costly damage arises.

Can a water hammer go away on its own?

Water hammer rarely goes away on its own; it's a serious plumbing problem you should address. Pipes can sustain damage from repeated impact, resulting in leaks or burst pipes. Fixtures like faucets and valves can also be affected by water hammer stress, leading to wear and tear or even failure over time.

Is a water hammer an emergency?

No, a sound is of course not dangerous—but what it represents can definitely have a heavy negative influence on your pipes. The effect of the shockwaves can damage the pipes and knock them loose, and also damage taps, faucets, and appliances. Enough force from water hammer can even cause pipes to burst.

How do you fix a knocking hot water pipe?

Air gets caught in the pipes, causing them to shake. To fix this, all you need to do is to turn off the main water pipe in your home completely. Then go to every faucet and hose in the house and open it fully, allowing all of the water standing in the pipes to drain out.

How much does it cost to flush a hot water heater?

Expect a pro to charge you between $75 and $200 to come to your home to flush your water heater, depending on where you live. While this cost deters many homeowners from performing this annual maintenance, it can extend the water heater's lifespan by years, making it worth the additional cost.

What is the life expectancy of a water heater?

While today's water heaters are better designed than older models, they still require regular maintenance in order to prolong their lives. With regular inspection, draining, and flushing, you can expect a gas water heater to last anywhere from 8-12 years and an electric water heater to last anywhere from 10-15 years.

Is it bad if my water heater is knocking?

Signs Your Water Heater Needs Repair

If any of the following is happening along with the knocking, it's time to call Schaafsma: Knocking, banging, or popping sounds can mean sediment buildup, water hammer, or heat trap issues. Inconsistent water temperatures or a lack of hot water.

How do I stop my heater from knocking?

Bleeding your radiators will release any air that may be trapped inside. When air gets into your heating system, it can cause a banging noise because it increases the pressure in the system. Releasing pressure by bleeding the pipes of excess air can stop the banging noise from occurring.

What does knocking sound on the heat pipe mean?

2) Trapped Air in the Pipes

Trapped air in the pipes, also called airlocks, can be a major cause of noisy heating pipes. The airlocks or air bubbles in your pipes create a loud sound that can sound like banging, knocking, or clunking.

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