Why Is My Hot Water Heater Making a Rumbling Noise? Causes And Fixes You Shouldn't Ignore

That deep, low rumbling coming from your water heater is hard to ignore - it's a sign that something is wrong. The good news is that the cause is usually identifiable, and in many cases, it is fixable before things get worse.

What Causes a Rumbling Water Heater?

The most common culprit behind a rumbling water heater is sediment buildup at the bottom of the tank. Over time, minerals in the water - especially in areas with hard water - settle and collect inside the tank. As the water heats up, it gets trapped in the sediment layer and essentially starts to boil underneath it, creating that familiar rumbling sound or kettle-like noise.

This process reduces efficiency, forces the burner or heating element to work harder, and can eventually lead to overheating or even a leak. For older water heaters, this kind of sediment buildup is especially common and worth taking seriously.

Both electric and gas water heaters are susceptible to this issue. If your water heater makes loud popping or bubbling sounds along with the rumbling, sediment in the tank is almost certainly the cause.

How to Drain and Flush a Water Heater

One of the best ways to address sediment buildup is to drain and flush the water heater. Here is a general overview of how it works:

• Turn off the power or, for a gas water heater, set the heater's gas valve to the pilot light setting.

• Turn off the water supply by closing the cold water supply valve or the supply valve near the unit.

• Connect a hose to the drain valve at the bottom of the tank and run it to a basement drain or outside.

• Open a hot water faucet somewhere in your home to allow air in so water flows out smoothly.

• Open the cold water inlet briefly once the tank is completely drained so a stream of water flows through and flushes out remaining sediment.

• Turn the water back on and refill the tank; restore power once the tank is full.

  
  

This process helps clear sediment from inside the tank and can restore normal water temperature performance. If you are unsure about any step, it is always safer to call a professional rather than risk a leak or water damage.

Other Sounds Coming From Your Water Heater

Not every noise is sediment-related. A hiss could point to a drip near the relief valve or a slow leak around the water line. If you notice sounds coming from your water heater along with visible moisture, that is a sign to call a plumber right away.

A knocking or ticking noise when water flows often comes from pipe expansion or other components expanding as they heat. Many newer units are designed to open and shut components more quietly, so unusual sounds in an older unit deserve attention.

For a deeper look at your options, check out our guide on tank vs. tankless water heaters for Middle Tennessee homes, or explore whether heat pump water heaters are worth it in Middle Tennessee.

When to Call a Professional Plumber

If flushing doesn't stop the rumbling, or you notice a leak, pressure issues, or water appearing where it shouldn't, bring in a licensed plumber. Noisy water heaters that also show signs of corrosion, a failing relief valve, or a compromised flue need a technician with the experience to diagnose what is specific to your situation.

Our team offers plumbing maintenance and repair services that cover water heater inspections, as well as professional water heater installation services when a full replacement makes more sense.

Conclusion

A rumbling water heater is not something to put off. Whether it needs a simple flush or a full inspection, acting early can protect your home's plumbing, lower energy costs, and extend the life of your water tank. If you are in Middle Tennessee and need help fast, Twenty Four Hour Plumbing is ready around the clock. Reach out through our 24/7 emergency plumbing services or call us at 615-785-3827 today.