Why is My Water Heater Making a Popping/Knocking Noise?

Simply put, sediment is the loose materials that accumulate at the bottom of the water tank. This is what leads to a water heater making popping noise. While you may think this sediment travels from somewhere and enters your tank, it’s actually caused by the water itself.



If the water in your area is “hard,” it contains a lot of minerals. While these minerals are actually good for us, your water heater doesn’t enjoy them. As the mineral-rich water enters your water heater, sediment will eventually settle at the bottom. Unfortunately, when there’s a water heater popping noise, your system probably isn’t working very efficiently. Also, this problem can lead to overheating, which could damage your tank.

If there’s only a small amount of sediment leading to a water heater making knocking noise, there’s probably no reason to worry. But if this sediment is in abundance, you should flush the unit ASAP.

When there’s a deep layer of sediment at the bottom of your tank, this can cause a number of problems, including:

• Overheating, which could damage the steel tank.
• Water tank leaks
• Water displacement, leading to less available hot water. 
• Sediment covering the heating element (only in electric water heaters)
• Higher water heating bills, caused by lower system efficiency.



If you have never had your tank flushed and you’re still hearing the water heater popping sound, there could be a large amount of sediment in your tank. You may choose to have your water heater serviced by a skilled professional.

As the heating element heats up the water in your tank, steam is created. When there’s sediment trapped at the bottom, the bubbling noise is the steam trying to escape the sediment. The same process happens when you boil water on the stove; the steam will try to push up the covered lid.

As the sediment settles at the bottom of your tank, this is also the location of the heating element. If water gets caught between the sediment and heating element, that water will heat up, steam, then try to escape through the layer of sediment. This is what causes the water heater knocking sound.



While a little bit of sediment is no reason to worry, you don’t want too much of it. When a water heater struggles to heat water properly, it will run longer—meaning less efficiency. This issue can even cause the water tank to overheat, which could cause costly damage to the tank’s inner lining.

When there’s a water heater making popping noise, the sound can drive the whole family crazy. And not only is it incredibly annoying, but the issue could also be damaging your water heater. Luckily, there’s a pretty simple solution you can complete on your own. This involves flushing the system. You can complete this yourself or call a professional.

Flushing your water heater is a simple process that only takes around 30 minutes. 

Here are the steps you should take:

1. Turn the control knob to “pilot” on your water heater. If you have an electric unit, turn off the water at your circuit breaker. 
2. Turn off your water supply. You can do this at the cold water ball valve or cold water lever.
3. Allow the system to cool off for about 30 minutes.
4. Attach a garden hose to the water heater’s drain valve, found at the bottom of the tank.
5. Place the other end of the hose somewhere where the water can safely drain.
6. Flip up the pressure relief valve, located near the top of the tank.
7. Turn the drain valve open. You may need pliers to turn the small slot on the valve.
8. Allow the water to flush out completely.
9. Turn on the cold water valve to remove any remaining sediment.
10.  When the water starts to run clear, close the valve, then let the cold water fill the tank.
11. After the tank is full of water, power the water heater back on.

While this is a pretty straightforward process, you could also hire a professional. Plumbers and HVAC specialists handle these services for a living, so call them today for a speedy and dependable solution.

If you have a water heater making popping noise, flushing the system could be just what you need. Not only will this eliminate that annoying water heater popping sound, but it can also result in greater system efficiency.