Why Is My Water Heater Making Popping or Rumbling Noises?
July 27, 2026
If your water heater has started popping, rumbling, or crackling like it's cooking popcorn in the basement or utility closet, you're not imagining things — and it's not going to fix itself. In almost every case, that noise is sediment buildup inside the tank, and it's a sign your water heater is working harder than it should.
Here's what's actually happening, why it matters, and what to do about it.
What Causes the Popping and Rumbling Sound?
Over time, minerals in your water — calcium, magnesium, and other sediment — settle at the bottom of your water heater tank. This happens in every water heater eventually, but it happens faster in areas with hard water, which is common throughout East Arkansas.
Once that layer of sediment builds up, it sits between the burner (or heating element) and the water itself. When the burner fires, water gets trapped underneath and inside that sediment layer. As it heats up, it turns to steam and forces its way up through the sediment, creating the popping, rumbling, or knocking sound you're hearing.
The thicker the sediment layer, the louder — and more frequent — the noise tends to get.
Is This Actually a Problem, or Just Annoying?
It's a real problem, not just a noisy nuisance. Sediment buildup causes several issues that compound the longer it's left alone:
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Reduced efficiency — Your water heater has to work harder and longer to heat water through that sediment layer, which drives up your energy bill.
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Less hot water — Sediment takes up space in the tank, meaning less room for actual water.
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Faster wear on the tank — The extra heat and stress on the tank bottom can shorten its lifespan significantly.
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Increased failure risk — In gas water heaters, the popping is caused by literal small steam explosions inside the tank. Left unaddressed long enough, this can stress the tank and fittings.
A water heater that's rumbling today is a water heater that's more likely to leak, fail, or need early replacement down the road.
Other Noises to Watch For
While popping and rumbling almost always point to sediment, a few other sounds are worth knowing:
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Ticking or tapping — Often just water flowing through pipes as they expand with heat; usually harmless.
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Hissing — Can indicate a small leak or condensation dripping onto the burner.
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High-pitched whining or screeching — Often related to a valve, such as the pressure relief valve.
If you're hearing anything beyond a light popping/rumbling — especially hissing or whining — it's worth having a plumber take a look sooner rather than later.
Can You Fix Sediment Buildup Yourself?
For minor buildup, a tank flush can help — draining the tank to clear out loose sediment. Many manufacturers recommend flushing a water heater once a year to prevent buildup from getting out of hand.
That said, once sediment has been sitting for a long time, it can harden and compact at the bottom of the tank. At that point, a standard flush may not fully clear it, and in older tanks, flushing can sometimes reveal or worsen existing leaks that the sediment had been quietly masking. If your water heater hasn't been flushed in a few years, it's worth having a licensed plumber inspect it before you attempt this yourself.
When to Call a Professional
Give us a call if:
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The popping/rumbling has been going on for more than a few days
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You notice reduced hot water along with the noise
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Your water heater is more than 6–8 years old and has never been flushed
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You see any rust-colored water, moisture, or pooling near the tank
Our licensed plumbers can flush the tank, inspect for underlying wear, and let you know honestly whether a flush will solve the problem or whether it's time to start thinking about water heater repair or replacement.
Prevent It From Coming Back
The best fix is prevention. Having your water heater flushed annually — ideally paired with a broader home maintenance check — keeps sediment from building up to the point of causing noise, inefficiency, or damage in the first place. If you're already on a maintenance plan for your HVAC system, ask about adding your water heater to that same routine visit.
Hearing popping or rumbling from your water heater in Wynne, Jonesboro, Searcy, Cabot, Beebe, Marion, or West Memphis? Mohr Air Conditioning has been keeping East Arkansas homes comfortable — and now leak-free — since 1968. Our licensed plumbers can flush, inspect, and repair your water heater, often the same day.
Frequently Asked Questions
Is a popping water heater dangerous? It's not usually an immediate danger, but it signals sediment buildup that reduces efficiency and increases the risk of tank damage or early failure over time. It's worth addressing rather than ignoring.
How often should I flush my water heater? Most manufacturers recommend flushing once a year, though homes with hard water — common across East Arkansas — may benefit from more frequent flushing.
Will flushing my water heater stop the noise? In many cases, yes. If sediment has hardened significantly, a professional inspection is the best way to know whether a flush will fully resolve it.