Quick answer
Popping or rumbling from a water heater is usually sediment on the bottom of the tank, with water trapped under it boiling as the tank heats. Flushing the tank removes loose sediment. Sizzling on a gas tank can mean water dripping on the burner, so check under the tank. Banging in the pipes when a tap shuts is water hammer. A relief valve that hisses or drips means the pressure or temperature is too high and needs a plumber the same day. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed October 27, 2026· Next review Apr 2027
Most water heater noises come from sediment: minerals from the water settle on the bottom of the tank, water gets trapped under the layer, and it pops and rumbles as the burner or element heats it. The noise itself is not dangerous, but it means the tank is working harder and the bottom is running hotter than it should. A few other sounds point to something else, and one of them is a reason to call the same day.
What the Sound Means
| Sound | Likely cause | What to do |
|---|---|---|
| Popping or rumbling while heating | Sediment on the bottom of the tank | Flush the tank, or have a plumber do it |
| Crackling or sizzling (electric) | Sediment on the lower element | Flush; the element may need replacing |
| Sizzling on a gas tank | Water dripping onto the burner: condensation, or a leak | Check for water under the tank |
| Knocking or banging in the pipes when a tap shuts | Water hammer | Plumber: hammer arrestor or pressure check |
| Ticking | Pipes expanding as hot water flows | Usually harmless |
| Screeching or whistling | A partly closed valve or a relief valve under pressure | Check that the cold supply valve is fully open; call if it continues |
| Hissing from the relief valve, or water from its pipe | Pressure or temperature too high | Call a plumber the same day |
Flushing a Tank
Flushing removes loose sediment. The steps for most tanks:
- 1Turn the gas control to pilot or switch off the breaker.
- 2Close the cold supply valve at the top of the tank.
- 3Attach a garden hose to the drain valve at the bottom and run it to a floor drain or outside.
- 4Open a hot tap upstairs, then open the drain valve and let it run until the water clears.
- 5Close the drain, refill the tank with the hot tap open until water flows steadily, then turn the heat back on.
If the drain valve is plastic, old or will not close fully, or the tank has never been flushed in many years, a plumber is the safer choice: a drain valve that will not reseal leaves you with a leak.
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
When the Noise Is a Warning
Popping in a tank that is also slow to heat, rusty water from the hot taps or water around the base points to a tank near the end of its service life. Water around the base is covered in our guide to a leaking water heater.
What a Repair Costs
HearthDry's figures put a valve or fitting repair at $100–$400 and a replacement, installed, at $900–$4,500 depending on the type. See the water heater repair page.
When to Call
Call if flushing has not quieted it, the relief valve hisses or drips, or water is collecting under the tank. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
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Frequently Asked Questions
Why is my water heater popping?
Sediment has built up on the bottom of the tank, and water trapped under it boils and pops as the burner or element heats.
Is a noisy water heater dangerous?
Popping from sediment is not dangerous in itself, but it means the tank is working harder. A hissing or dripping relief valve is a reason to call a plumber the same day.
Will flushing a water heater stop the noise?
Often, if the sediment is loose. Hardened scale that has built up for years may not flush out, and an old drain valve may not reseal.
What causes knocking in the pipes when a tap is turned off?
Water hammer: the moving water stops suddenly. A plumber checks the pressure and may fit a hammer arrestor.
Sources
Methodology: How we source and verify data · Report an error
Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.
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