Why Is My Water Heater Making Strange Noises?

Water heaters are supposed to be one of the quietest appliances in the house. When they start making noise, it's worth paying attention, because the specific sound usually points to a specific cause.

Popping or rumbling: sediment buildup

This is the most common noise complaint, and it comes from mineral sediment that's settled at the bottom of the tank over months or years. As the burner or heating element warms the water, it heats trapped pockets under and within that sediment layer, and the resulting steam bubbles pop and rumble their way to the surface. It's often described as sounding like the tank is boiling, which is essentially what's happening in miniature.

What to do: a full tank flush (see our guide on flushing a water heater) often reduces or eliminates this noise if caught early. If the sediment layer has hardened significantly, flushing may only partially help, and it's a sign the tank has some real wear on it.

Ticking: thermal expansion

A rhythmic ticking, especially right after hot water use, is usually just pipes expanding and contracting as hot water moves through them and as the tank heats and cools. This is one of the more benign noises on this list. It's the sound of metal responding to temperature changes, not a sign of internal damage.

What to do: if the ticking is mild and consistent, it's typically nothing to worry about. If it's new, loud, or paired with visible pipe movement, it may be worth checking that pipe straps and hangers are still secure.

Whining or screeching: the inlet valve

A high-pitched whine, particularly while the tank is filling after use, often traces back to the cold water inlet valve. Mineral deposits or a partially closed valve can restrict flow enough to create a whistling or whining sound as water is forced through a narrower opening than intended.

What to do: check that the inlet valve is fully open. If it already is and the whine persists, the valve itself may need cleaning or replacement.

Crackling or sizzling: the heating element or burner

On electric units, crackling often means sediment has built up directly on the heating element, causing it to overheat unevenly as it tries to heat through the buildup. On gas units, a sizzling sound can indicate condensation dripping onto the burner. Either way, this points to a specific component under stress rather than a general maintenance issue.

What to do: this one is less DIY-friendly than the others. Electric heating elements coated in hardened sediment often need to be removed and either descaled or replaced, and that means draining the tank and working with electrical components.

Matching the sound to the severity

• Ticking from thermal expansion: low concern, monitor it.
• Whining from the inlet valve: low to moderate concern, easy to check yourself.
• Popping or rumbling from sediment: moderate concern, addressable with a flush.
• Crackling from the heating element or burner: higher concern, often needs component-level repair.

If a flush doesn't quiet things down, or you're hearing crackling and sizzling rather than the more benign ticking and popping, it's a good sign to have ProFlow Plumbing take a listen before a stressed component fails outright.