Water Heater Making Noise? Causes & Fixes

Your water heater is making noise again. Maybe it’s a subtle humming that you didn’t notice until now. Maybe it’s a loud banging that sounds like someone’s hitting your tank with a hammer. Maybe it’s a pop or crack that makes you jump every time you shower.

The first instinct is usually panic. Is the tank about to explode? Is it dangerous? How much is this going to cost?

The good news: most water heater noises aren’t emergencies. The bad news: some of them are early warning signs that something needs attention. Understanding what different noises mean is the first step to knowing whether you can ignore it, fix it yourself, or call a professional.

Let’s break down what’s actually happening inside your tank when it starts making noise.

The Most Common Noise: Rumbling and Popping

This is by far the most common water heater noise, and it’s almost always the same cause: sediment buildup at the bottom of the tank.

Here’s what’s happening inside. Over months and years, minerals from your water supply settle at the bottom of your tank—calcium, magnesium, rust particles, and other sediment. As your heating element or burner heats the tank, the water beneath that sediment layer gets extremely hot. Sometimes it gets so hot it turns to steam. That steam bubbles up through the sediment layer with force, creating a popping or rumbling sound. You’re literally hearing tiny explosions of steam pushing through sediment.

This noise is annoying but not immediately dangerous. However, it’s a sign that your water heater needs maintenance. Sediment reduces efficiency, makes your unit work harder, and accelerates wear. The more sediment you have, the louder and more frequent the noise becomes.

The fix is simple: flush your water heater. A professional flush costs $100–$200 and takes about an hour. A DIY flush costs about $30 in supplies if you’re comfortable with basic plumbing. After flushing, the noise usually stops entirely or drops dramatically.

If the rumbling and popping get worse over weeks or months despite flushing attempts, it suggests your tank is heavily damaged internally. That’s a sign you need replacement rather than repair.

The Hissing Sound: What It Means

A continuous hissing sound from your water heater is different from popping and rumbling. Hissing usually means steam or air is escaping somewhere.

The most common cause is a failing temperature and pressure relief valve (often called the T&P valve). This valve is a safety feature designed to release pressure or temperature if either gets too high. When it starts to fail, it can leak or release small amounts of steam, creating a hissing sound.

In most cases, a small amount of hissing from the relief valve is relatively normal, especially if it happens briefly when the heater is actively heating. The valve opening and closing creates that sound. It usually stops once the heating cycle completes.

If the hissing is constant and loud, there’s a problem. The valve might be stuck partially open, or it might be failing. This needs professional attention because a stuck relief valve can cause pressure to build dangerously inside the tank.

Another source of hissing is a leak at one of the water connections (inlet, outlet, or drain valve). If you hear hissing and see water dripping, locate where the water is coming from. If it’s a connection, it might just need tightening. If it’s leaking from the body of the tank itself, the tank is failing and needs replacement.

The Crackling or Sizzling Sound: Sediment and Heat

This one sounds like bacon frying or a campfire crackling. It’s usually sediment-related but slightly different from the popping sound.

When you have a layer of sediment on the bottom of your tank and the heating element gets hot, sometimes water gets trapped under that sediment. As that trapped water overheats, it turns to steam and creates tiny pockets of heat. When cooler water above touches those hot pockets, you get a sizzling or crackling effect—like water dropping onto a hot pan.

This is also caused by sediment and fixed by flushing. Once you remove that sediment layer, the water heats evenly and the noise stops.

If you’re hearing crackling and the water heater is new or relatively clean, it might be something else. Water can also create this sound if it’s aerated (has tiny air bubbles in it). This is usually temporary and stops on its own as the air works out of the lines.

The Banging or Knocking Sound: Water Hammer

This is the scary one because it sounds like something’s seriously wrong. A loud bang from your water heater, sometimes followed by shaking or vibration, is called water hammer.

Water hammer happens when water moving through pipes suddenly stops or changes direction quickly. When a valve closes abruptly (like when a washing machine stops filling or a faucet is turned off suddenly), the moving water has nowhere to go and crashes into the valve or pipe fitting. That impact creates the banging sound.

Water heater connections are usually located where water hammer can be transmitted directly to the tank, so you hear it clearly. It sounds like someone’s hitting your heater with a hammer, which is why it’s called water hammer.

Water hammer is annoying but usually not dangerous to the heater itself. However, it does indicate your plumbing system could use a water hammer arrestor—a small device installed on the water line that absorbs the shock of sudden pressure changes. This costs $50–$150 to install and solves the problem.

Important note: if the banging is coming specifically from inside your tank and sounds metallic, like something loose inside is hitting the walls, that’s different and more serious. That suggests something internal is broken and needs professional inspection.

The Whistling Sound: Air or Water Flow Issues

A whistling sound, especially one that changes pitch or stops when you use hot water, usually means air is entering the system where it shouldn’t.

If you recently had plumbing work done, or if you flushed your water heater, air in the lines is normal and temporary. Run hot water for a few minutes and the air will purge out.

A persistent whistling could indicate a partial clog somewhere in the water line, causing water to rush through a narrowed passage and create that whistling sound. This usually affects only hot water flow, not cold water.

Another cause is a failing mixing valve if you have one installed. Mixing valves balance hot and cold water, and when they start to fail, they can create whistling or squealing sounds.

The whistling usually goes away on its own after you’ve used the system for a while. If it persists for more than a few hours after flushing or plumbing work, call a plumber.

The Humming Sound: Electric Element Vibration

If you have an electric water heater, a humming sound is usually the heating element vibrating as it operates. This is completely normal. Every electric water heater hums slightly when the element is actively heating water.

The humming gets louder if sediment has built up around the element, because the sediment forces the element to work harder to transfer heat. Once you flush the tank, the humming usually becomes quieter because the element doesn’t have to strain as much.

If the humming is extremely loud or sounds strained, it could indicate the element is about to burn out. If you hear humming but there’s no hot water being produced, the element has failed and needs replacement.

The Ticking or Clicking Sound: Thermal Expansion

When water heats, it expands. Your water heater accounts for this expansion, but the pipes and connections around it also expand and contract with temperature changes.

A ticking or clicking sound, especially one that happens during heating cycles and stops when the heater isn’t running, is usually the result of pipes expanding against brackets, straps, or nearby structures. It’s the sound of metal expanding and contracting as temperature changes.

This is annoying but not dangerous. If it’s loud enough to bother you, a plumber can add more insulation or adjust how the pipes are supported to dampen the sound. This is a cosmetic fix, not a necessary repair.

The Silence After Noise: Did It Fix Itself?

Sometimes your water heater makes noise for a while, then stops. This is actually pretty common and usually explains itself.

If the noise was popping or rumbling and then stopped after you used a lot of hot water, sediment has been loosened and flushed partially out. You might get temporary relief. However, if you don’t fully flush the tank, the noise will return once sediment settles again. It’s not fixed; it’s just quiet temporarily.

If noise stops after several weeks, it might indicate the problem self-resolved (air worked out, water aeration stopped, sediment settled in a way that reduces noise). Or it might mean the situation is getting worse internally but the noise expression changed.

The safest approach: if your water heater made concerning noise but it stopped, don’t assume everything’s fine. Have it inspected by a professional to determine what was happening.

Which Noises Mean You Should Call a Plumber Immediately

Not all water heater noises are created equal. Some are annoying but harmless. Some indicate a problem that will get worse if ignored. Some are actual emergencies.

Call a plumber immediately if your heater is making loud banging combined with shaking or vibration of the tank itself. That suggests internal damage or extreme pressure buildup.

Call immediately if you hear a loud hissing and see water dripping from the tank body (as opposed to the connections). That’s likely a failing tank. You could have a flood on your hands soon.

Call immediately if the heater smells like burning, or if you hear a noise combined with a strong smell. That could indicate electrical issues or something actually burning inside.

Call immediately if you have no hot water and the heater is making loud popping, banging, or other intense noise. The noise combined with loss of function suggests a significant internal failure.

Call within a day or two if the noise is moderate, there’s still hot water, and you don’t see any leaks. These are usually maintenance issues that need addressing but aren’t emergencies.

If the noise is minor and you have hot water, you can probably wait until a convenient time to schedule service. Humming from an electric element, minor popping that comes and goes, or ticking from thermal expansion—these aren’t urgent.

What You Should Not Do

Don’t ignore persistent loud noises hoping they go away. They won’t. Noises indicate a problem, and that problem will get worse over time.

Don’t assume because you still have hot water that the heater is fine. Loss of hot water isn’t always the first sign of failure. Noises and leaks often come first.

Don’t try to stop noise by adjusting the thermostat. Lowering the temperature might reduce some sediment-related noise temporarily, but it doesn’t solve the underlying problem.

Don’t panic immediately at the first noise. Some sounds are completely normal. A little humming from an electric heater, occasional pops from sediment, or temporary whistling after plumbing work—these aren’t emergencies.

Don’t assume a plumber can fix any noise. Sometimes the noise indicates a problem that requires tank replacement, not repair. A professional diagnosis tells you which situation you’re in.

Prevention: Keep Your Water Heater Quiet

The best way to avoid water heater noise is preventive maintenance.

Flush your tank annually. This removes sediment before it builds up enough to create noise. Flushing is the single most important maintenance task. People who flush regularly almost never deal with popping or rumbling.

Have the temperature and pressure relief valve tested annually. A functioning relief valve prevents pressure buildup and the noises that come with it.

Install a water hammer arrestor if you don’t have one. If you’re hearing banging when water fills quickly or valves close suddenly, this solves it permanently and costs less than $200 installed.

Check the tank support and pipe strapping. Make sure your heater is securely mounted and pipes are properly supported. Loose mounting increases vibration and noise transmission. Tightening straps and brackets can reduce ticking and humming sounds.

Monitor your water heater routinely. Every month or so, listen to it when it’s actively heating. Notice changes in sound. A gradual increase in noise intensity over weeks indicates an emerging problem. Sudden new noise indicates something just happened.

When Noise Means Replacement Time

Sometimes noise indicates your water heater has reached the end of its useful life, and repair isn’t the right answer.

If your heater is over 10 years old and making significant noise, especially if flushing doesn’t help, replacement is probably the better choice than repair. The cost of repair plus the ongoing risk of failure makes replacement more economical.

If the noise is accompanied by rust-colored water, that indicates internal corrosion. No amount of repair will fix corrosion. The tank is deteriorating internally.

If you’ve flushed recently and the noise is getting worse, not better, sediment isn’t the problem. Something else is failing inside, which usually means the tank has reached the end of its life.

A professional plumber can assess whether your heater should be repaired or replaced based on its age, the noise type, and other factors. That assessment usually guides your decision.

DIY Diagnostics: What to Listen For

You don’t need special equipment to diagnose your water heater. Your ears are pretty good at this.

Place your ear near (not touching) the tank and listen carefully. Is the sound coming from inside the tank, from the pipes, or from the connections? Sounds from inside the tank are usually more serious than sounds from pipes or connections.

Note when the sound happens. Does it occur only during heating cycles? Only when you’re using hot water? All the time? When exactly the noise happens narrows down the cause.

Record it on your phone if possible. Play it for a plumber before they arrive. This helps them diagnose faster because they immediately know what they’re listening for.

Check for leaks while listening. Is water dripping anywhere? Leaks combined with noise is more serious than noise alone.

Feel the tank and pipes carefully (avoid the hot surface of the tank itself). Is vibration happening? Vibration combined with banging suggests water hammer or mounting issues.

Related Diagnostics and Maintenance

Water heater noise doesn’t exist in isolation. It’s often connected to other issues worth understanding.

• How to Flush (and Drain) a Water Heater — The most common fix for noise
• Why Is My Water Heater Not Producing Hot Water? — When noise is accompanied by loss of function
• When Should You Replace a Water Heater? — Determining if repair or replacement makes sense
• Water Heater Replacement Cost — What to budget if replacement is needed
• Water Heater Parts You Can Replace — Relief valve and element replacement options

The Bottom Line: Noise Is Information

Your water heater is trying to tell you something when it makes noise. The key is understanding what it’s saying.

Most water heater noise is caused by sediment buildup, which is fixable with a flush. Some noise indicates water hammer in your plumbing, which is annoying but not dangerous to the heater. Some noise is just normal operation (humming, occasional pops, minor sounds).

The noises that matter are the loud ones combined with other problems: leaks, loss of hot water, burning smells, or constant intense sounds. Those indicate something that needs professional attention soon.

The best strategy is simple: listen to your water heater regularly so you know what normal sounds like. When something changes significantly, that’s when you investigate further or call a professional. Catching problems early, before they become emergencies, saves you money and stress.

Most water heater noise problems are preventable or easy to fix with regular maintenance. Flush annually, have the relief valve checked, and keep an eye on your heater’s condition. Do that, and you’ll probably never need to worry about what your water heater is saying.

Professional Diagnosis in New Jersey

If your water heater is making noise and you’re not sure what it means, Doctor Water Heater can diagnose the issue quickly and recommend the right fix—whether that’s a simple flush, valve replacement, or full replacement.

We listen to the noise, inspect your system, and give you an honest assessment of what’s happening and what it will cost to fix. No guessing, no surprises.

Get Professional Diagnosis Today
Don’t let water heater noise become a bigger problem than it needs to be.

Water heater noise diagnosis varies by sound type and system condition. If you’re uncertain about any noise your water heater is making, contact a licensed plumber for professional assessment.