Is Hot Water Heater Knocking Dangerous? Find the Answer Here

A water heater knocking noise could startle everyone. But, importantly, what does it mean? Is hot water heater knocking dangerous? This knocking, often a result of sediment buildup at the bottom of the water heater’s tank, can be a warning sign of potential issues.

The water heater usually makes a low voice like a humming when it is used. So, a strange knocking sound could mean some fault in your unit that could lead to a broken machine.

Is Hot Water Heater Knocking Dangerous?   

A knocking sound from the water heater is not a normal thing. The sound usually indicates that the tank on the water heater is collecting a thick layer of sediment. Regularly flushing your water heater can help prevent this sediment buildup, which often manifests as a popping noise during heating cycles.

Read also: Why Your Water Heater Sounds Like a Tea Kettle

The sediment is usually formed by lime and calcium. This collection of thick mineral layers could make the water heater not work as it used to. It can damage your unit and also raise your electricity bill.

is hot water heater knocking dangerous

These problems could happen since water could be trapped in the sediment. For example, the water will be trapped at the bottom of the tank on the heating burner spot. If so, when the gas starts to boil the water, the bubbles could escape the layer of sediment.

The sediment will not make your water heater explode. However, it could lead to other problems that are quite troublesome. The sediment can make the component overheat.

If it continues to do so, over time, your unit will need to be replaced by a new one. The heating element, when covered in sediment, becomes less efficient and can contribute to the knocking sound.

In addition to sediment buildup, other factors, such as a malfunctioning thermostat or a faulty heating element, can also contribute to the knocking noise. It’s crucial to assess these components during maintenance checks.

The knocking sound can also be exacerbated when the water heater’s tank is not properly insulated. Insulating the tank can help reduce the noise and improve the efficiency of the unit.

What Happens If I Do Not Maintain the Condition of the Water Heater?

Maintaining the water heater’s condition, especially by regularly flushing your water heater to remove sediment at the bottom, could prevent knocking sounds from appearing. If you’re unsure about how to proceed, consulting professional plumbers can ensure that the job is done safely and effectively.

Take some time to get experts to check your component or the plumbing system to keep it in a better condition.

If you fail to do so, there will appear to be some problems at your unit. Here are the things:

  • First, the sediment will eventually cause leaking on your unit. Hence, hot water could damage your house. This could be dangerous since the hot water could potentially harm your loved ones at home.
  • Second, if the sediment on the water heater is getting bigger, there will be less room for hot water in your unit. Therefore, you will find less hot water coming out of the component. It is pretty uncomfortable, especially in cold weather.
  • Then, if sediment build-up gets out of control, it could break down the water heater. The sediment can insulate the water from the heating element, leading to overheating and the characteristic knocking or popping noise. If it happens, you have no choice but to buy a new one or repair the damage. Either one is a cheap option.

Hot Water Heater Fix Steps

If you want to fix the troublesome knocking sounds or any other noise from your water heater, you could follow these steps. Remember, while some maintenance can be a DIY task, professional plumbers best handle complex issues.

Take note that using a service from an expert is better. However, if the condition is not favorable, always try to do it yourself:

  1. Turn off the water heater.
  2. Use gloves so you do not burn yourself.
  3. Turn off the cold water valve.
  4. Let the unit cool off for several minutes. Try to be patient and wait at least 30 minutes so you don’t burn your hands.
  5. Then, connect the drain valve with a garden hose at the bottom of the tank.
  6. Place the end of the hose to drain.
  7. Turn the small slot on the valve to open the drain on the water heater.
  8. Drain the water.
  9. Flush out the sediment using a cold water valve.
  10. If the water starts to have a brief appearance, close the drain and fill the tank with cold water.
  11. Turn the heating on again.
  12. Check if there is any trouble with the unit.
  13. Try to do this regularly to prevent sediment build-up on your water heater.

Regularly inspecting the anode rod in your water heater is also important. A corroded anode rod can accelerate sediment buildup, leading to more frequent knocking sounds.

If you’re experiencing a persistent knocking noise, it might be a sign that your water heater requires more comprehensive servicing or even replacement, especially if it’s an older unit.


Is a hot water heater knocking dangerous? The answer is yes. It is dangerous if you do not repair it in time since it could cause the unit to break down. Therefore, always maintain and repair your water heater so it can be used longer.

Remember, while some DIY maintenance can be performed, it’s always safest to consult with a professional when dealing with complex water heater issues to ensure your safety and the longevity of your appliance.

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Jhon Thermon is a skilled author and water heater expert with years of experience in the field. He has authored several articles and books on various aspects of water heater installation, maintenance, and repair.