Why is My Water Heater Making a Popping or Knocking Noises?

Have you been hearing a strange noise coming from your water heater? Does it make a violent knocking or a swift popping noise?

You’re probably a bit concerned with ANY noise coming from your water heater, since they are responsible for keeping you both safe and warm. If you’re hearing either of those startling noises, here’s what you need to know. 

Most of the time when your heater makes popping noises it’s because have sediment buildup. However, a bad heating element, a faulty thermostat, or a simple leak could also be the reason why your heater is making noises. While all of these are entirely different, some are repairable at home by replacing parts or cleaning out the residue built up inside the tank.

While some issues may require professional help such as a leak that can’t be fixed properly at home, you can easily find the source of the problem safely and effectively. 

Let’s discuss the possible reasons your water heater is making alarming noises. This article will touch on some common issues associated with a popping or knocking noise and how to diagnose the problem.

From cleaning residue to replacing your thermostat, we will cover the basics when it comes to identifying the cause of these noises coming from your water heater. 

Why is Your Water Heater Making Noises? 

When your water heater is making a noise not normally heard while functioning normally, it can sometimes be alarming.

Rest assured, these noises do occur with common, minor problems so it isn’t always a catastrophic issue. Here are some of the main reasons you might be hearing unsettling noises coming from your water heater: 

You Have a Residue Buildup 

Water sediments are tiny solid particles that don’t properly dissolve in water and settle at the very bottom of the water heater. The buildup is due to the minerals found in all water types.

In addition to reducing the efficiency of its normal function, it can clog the water pathway, creating a reduced flow. In this case, you will start to notice a popping noise since your water flow is trapped under the lime deposits and buildup at the bottom of the tank. The good news is you can address this problem at home with a simple cleaning. 

Bad Heating Element 

A bad heating element is another common cause of the knocking noises that many homeowners experience with their water heaters. The knocking noise is usually the telltale sign for this exact issue. 

In this case, you may need the help of a professional to assist. They will use a special tool called a multimeter to measure the resistance of the element.

The heating element will sometimes fail due to sediment buildup, sudden power surges or a crack in the water heater. When troubleshooting during your diagnoses, you can find the heating element at the bottom of the tank on the inside typically. 

Broken Thermostat 

When you have a broken or damaged thermostat, you may also come across a loud, knocking noise. The thermostat is responsible for regulating the temperatures within your water heater. Once a thermostat is damaged or no longer functioning correctly, your water will heat unevenly, causing a disturbance within the system. 

To check out your thermostat, you can find it located typically at the bottom, front of a gas water heater. For electric water heaters, there are usually two thermostats- one at the top and one at the bottom. 

There’s a Water Leak 

Water leaks occur for a number of reasons- sometimes, and most commonly,  it’s due to dirty or broken valves.

A leak within the water line is a typical outcome of pressure within the system or faulty valves. In turn, electrical components that come in contact with the leak can cause the water heater to short circuit.

If you notice a leak, you will want to check the valves and search for the source of the leak. Be sure to look at both the top and bottom to find the location of your water leak. 

How to Clean Sediment From Your Water Heater 

If you’ve come to the conclusion that your water heater has formed some sediment buildup, the good news is that you can tackle this at home safely and effectively.

Removing the buildup means better water flow and no blockages, so your home will be heating efficiently and the noise will dissipate. Here are the steps to cleaning out the residue buildup to your water heater:

Step 1: Turn the Water and Electric Supply Off 

Turning off the water and electrical supply is the key to safely approaching the water heater. If you have an electric system, simply turn off the power switch. If you have a gas water heater, turn the thermostat to the pilot setting.

Now that your heating element is off, your water can cool down. Be sure that no one will need to run hot water during this time in the household. Additionally, you will want to turn off the cold water as well to ensure that no water is running during this time. 

Step 2: Drain the Water From Your Heater

Now that you’ve turned off the water supply, it’s time to drain all the water from your heater. Start by approaching your drain valve, located at the bottom side of the tank.

Attach a garden hose or or drain to the valve, and place the end of your hose inside a bucket. Turn the drain valve dial to allow the water to drain out into your bucket. 

Step 3: Flush the Water Heater 

As you continue to flush out your system, you’ll notice the piece of sediment flooding into your buckets. This may require a few fills and dumps before you reach the end. Once you have completely emptied the tank, you will want to do this process once more. 

To fill up your tank, turn the drain valve off and remove the house. Put your cold water back on and turn on your heating elements. Once you are full, you can repeat the process to ensure all the sediment has left your tank. 

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After flushing out your system twice, you can turn everything back on and let your water heat up.

You’ll want to wait roughly thirty minutes before you use any hot water in the house. By now, your water heater is now cleaned out of all unwanted debris and sediment, and the noises should disappear if that was the main cause of your problem. 

How to Fix a Knocking Water Heater? 

There are certainly several main causes that make a water heater create a loud, knocking noise as it heats your water and flows through your home.

In short, you may need to replace a thermostat, check and fix leaks or replace the heating element. Here are some quick ways to troubleshoot and replace the issues you may have with your water heater: 

Replace the Thermostat 

If your thermostat needs to be replaced, start by gathering your materials. You will need a multimeter, a new thermostat (this will require research on the manufacturer site) and safety glasses. Follow the simple process below:

  • Turn off your hot water heater
  • Remove the thermostat cover and set it aside. 
  • Touch the multimeter to a grounded metal object, such as the tank itself. Connect the second probe to each thermostat terminal and the terminal of both heating elements. This step is part of the safety- make sure there is zero voltage coming from the unit. 
  • Unplug the wires from the wall, paying close attention to how they are going to be reconnected. Remove the thermostat by carefully lifting it out. 
  • Carefully replace the thermostat and make sure it’s the perfect fit. Reconnect the wires as they were. Replace the protective cover with a new one. 
  • Lastly, change the temperature setting to a safe measurement for that model, which is typically 80-100 degrees fahrenheit. 
  • Activate the water heater as normal and test out the thermostat to ensure its working properly.

Stop Any Leaks 

If you’ve discovered your hot water heater has a leak, this can be addressed at home with the right parts. This will be dependent on where the leak is and what it entails.

If the leak is minor and you’ve been able to identify exactly the cause, you can research the proper parts and approach the problem with no issues. You may also want to check for loose valves, as they are commonly a culprit for water drainage.

For example, if you believe you have a faulty drain valve, check the following: 

  • Flush the system as shown above to ensure there is no sediment buildup. 
  • If your drain valve is the main suspect, gather your materials which include: a pipe wrench and new valve replacement. 
  • Tighten the drain valve with the wrench, ensuring there is no looseness. Sometimes a loose valve can be the cause of slow leaks. 

If tightening the valve doesn’t help, you may want to contact a professional about replacing the valve. 

Replace the Heating Element 

You only need three things to complete this easy replacement. Here is the quick process:

  • Grab a Phillip screwdriver, work gloves and an element removal socket to take out the faulty element. 
  • Turn off the electricity to ensure safety. 
  • Follow all the steps to drain your water heater. 
  • Disconnect the wires for the heating element. Remove the plastic shield to the heating element. 
  • Remove the heating element  using the element removal socket. 
  • Install the new heating element, ensuring all the wires are connected as they were before. Reinstall the plastic shield and cover to the water heater. 
  • Make sure the drain valve has been closed post draining. 
  • Refill your tank and restore power. 


Overall, it is easy to diagnose the problem when you hear a knocking or popping noise coming from your water heater. It is typically due to common issues such as slow leaks, faulty thermostats, sediment buildup or a bad heating element.

Luckily, all of these issues are pretty minor and can be handled either at home or with the help of a professional technician. If you can safely approach your water heater, a lot of these problems can be fixed in no time at all.

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