Plumbing guide · Mission Viejo, CA
Why Is My Water Heater Making Noise?
Why is my water heater making noise? Popping and rumbling usually mean sediment, hissing means steam or a drip on the burner, banging means pressure or loose pipes, and humming means an electric element. Match your sound below to find the cause and the safe next step.
(657) 681-2100- Name the soundPop, hiss, tick, bang, hum, whine or whistle.
- Note when it happensWhile heating, when a tap opens, or all the time.
- Follow the safe stepSome noises are harmless; a few mean stop and call.
Why is my water heater making noise? Sound by sound
- Popping or rumblingSediment on the tank floor, with water boiling underneath it.
- Hissing or sizzlingWater dripping on a hot burner, a leak or a relief valve venting.
- Ticking or creakingPipes and heat traps expanding as the water warms.
- Banging or knockingWater hammer when a valve closes fast, or loose pipes.
- Humming or buzzingAn electric element vibrating, or a loose part.
- High whine or whistleFlow squeezing past a partly closed valve or a scaled passage.
Why is my water heater making noise? Start with where the sound is
The location of a noise narrows the cause before you know anything else.
A sound map of a tank heater
Put your ear near the bottom, then near the top. Sounds that come from the base nearly always involve the burner, the elements or the sediment. Sounds at the top or along the pipes usually involve flow and pressure.
The rule of thumb: base noises are about heat, top noises are about water. That alone sorts most cases in a minute.
What each water heater sound means and what to do
Find the sound closest to yours. The right column is the safe first step.
| The sound | Usual cause | Safe first step |
|---|---|---|
| Popping, crackling or rumbling while heating | Sediment boiling under water | Plan a flush; see below |
| Sizzling or hissing on a gas unit | Water dripping onto the burner, or condensation | Look for a leak above; call if it continues |
| Hissing from a pipe on the side | Relief valve venting steam or pressure | Turn the thermostat down; call if it keeps venting |
| Ticking after use | Heat traps and pipes cooling or warming | Usually harmless |
| Banging when a tap closes | Water hammer | See the water hammer notes |
| Humming on an electric unit | An element vibrating or a loose bracket | Switch off at the breaker and call if loud |
| Whistling or whining | Flow through a partly closed valve or a scaled passage | Check the shutoff valves are wide open |
| Booming when the burner lights | Delayed ignition or a dirty burner | Turn the gas control off and call |
| Screeching from a tankless unit | Scale in the heat exchanger or a failing fan | Check the inlet screen; call if it persists |
If a sound arrives with water on the floor or a gas smell, stop reading and act: close the cold valve, switch the heater off, and call. Gas smell means leaving the house first; the guide on signs of a gas leak in your home explains what to do.
Popping and rumbling: the sediment story
If the noise is a rolling pop that starts a few minutes into a heating cycle, this is almost always the cause.
What is happening in the tank
Minerals settle from heated water onto the floor of the tank. Water gets trapped in the crust. When the burner or element heats it, the trapped water turns to steam and bursts up through the layer. That is the pop.
The thicker the crust, the louder the noise. Some tanks sound like popcorn. The crust also insulates the heat source, so a loud tank often runs less efficiently and wears faster.
In an area with hard water the crust builds quickly. The Santa Margarita Water District reports an average of about 256 ppm, and your tap can differ by address and by district. Look at your bill to see which district serves your home.
- A fresh popping tank, under 8 yearsA flush often quiets it; see how to flush a water heater
- Popping that returns within weeksHeavy crust that did not drain; a plumber can use a pump or an acid treatment
- A loud tank over 10 years oldThe crust may be hiding a worn lining; plan for replacement
- Popping with rust-colored waterInterior corrosion; the tank may be near its end
Hissing and sizzling: harmless condensation or a warning?
Hissing is the sound most owners worry about, and it is the one with the widest range of causes.
Three kinds of hiss
| When | Cause | Concern |
|---|---|---|
| Right after the burner lights, brief | Condensation on a cold tank burning off | Low |
| Steady sizzle at the base | A slow leak dripping onto the burner or element | High: shut off and call |
| From the side valve and pipe | The relief valve venting pressure | High: do not cap the valve |
| From a joint at the top | A small pressure leak at a fitting | Medium: close the cold valve and call |
A tank that sizzles at the base is telling you water is reaching the heat source. Do not wait. Close the cold valve above the heater, switch off the power or gas, and call water heater repair. If the tank itself is weeping, water heater replacement is the likely end of that story.
A relief valve that vents is doing its job. Something is wrong with pressure or temperature, so the cause needs finding.
Banging, knocking and water hammer
A bang when a tap or appliance shuts off is hydraulic, not thermal.
Why pipes bang
When a fast-closing valve, such as a washer or dishwasher, snaps shut, the moving water slams to a stop and the shock runs through the pipes. A loose pipe then knocks against a stud. The sound often seems to come from the heater simply because its pipes are close by.
Fixes are usually simple: secure loose pipes, add water hammer arrestors, or adjust the pressure. A pressure reducing valve that has failed lets house pressure climb and makes everything louder. Our page on low water pressure and the guide on why your water pressure is low cover the other end of the problem.
One more cause is thermal expansion. When water heats in a closed system, it needs somewhere to go. An expansion tank gives it room; without one, pipes can groan and the relief valve may drip.
- Bang when a washer shuts offWater hammer; arrestors can help
- Knock that follows hot water useA pipe loose in its strap
- Groan while the tank heatsThermal expansion in a closed system
- Bangs plus a dripping relief valveHigh pressure; have it measured
Humming, buzzing and whining
Steady tones come from vibrating parts or squeezed flow.
Which tone, which cause
| Tone | Where | Cause |
|---|---|---|
| Low hum | Base of an electric tank | An element vibrating in scale, or a loose mounting bracket |
| Buzz | Control area | A relay or contactor on the way out |
| High whine | Pipes near the heater | A shutoff valve partly closed |
| Whistle on hot only | Hot taps | Scale narrowing a passage or a worn valve |
| Rattle when the burner starts | Gas burner | A loose burner or heat shield |
Start with the cheapest check. Make sure every shutoff valve on the heater is wide open. A gate valve left half closed after a past repair is the classic cause of a whine. If that is not it, the next suspect is scale.
An element humming in scale is a sign the sediment story is also in play. Flushing helps. If the hum is loud or the breaker trips, switch the unit off and call.
Noise from a tankless water heater is different
A tankless heater has no sediment bed to boil, so its noises come from a different place.
Tank sounds vs tankless sounds
Tankless units have a fan, a burner, a flow sensor and a heat exchanger. A fan hum is normal. A rattling fan, a high-pitched squeal or a sound like a kettle just before water turns cold usually points to scale in the exchanger or a clogged inlet screen.
Descaling usually quiets a kettling tankless heater. The page on tankless water heaters explains upkeep, and the guide on tankless vs tank water heater compares the two designs.
What to do the day a water heater starts making noise
You can do these safe steps before anyone arrives.
Listen and locate
Note the sound, the spot and the moment it happens.
Look for water and smells
A wet base or a gas smell changes everything. Act on those first.
Check the valves
Make sure the cold shutoff and any hot shutoff are wide open.
Lower the thermostat
A lower setting reduces steam and pressure while you wait.
Call with details
Age, fuel, sound and when it started help a plumber give advice on the phone.
Stop and call at once if
The noise comes with water on the floor, a gas smell, a relief valve spitting steam, scalding water at the taps or a tripping breaker. Close the cold valve, switch off the power or gas, and call an emergency plumber.
Habits that keep a water heater quiet
Most noise is slow-building. A little routine upkeep keeps it from starting.
A quiet-heater routine
- Drain sediment yearlyThe single most effective habit, especially on hard water
- Test the relief valve twice a yearA valve that works is a valve that is not stuck
- Keep the straps snugPipes that cannot move cannot knock
- Treat the waterA softener cuts the scale that boils, hums and rattles; see water softener installation
- Do not set the thermostat too highHotter water means more steam under the crust
None of this takes more than a few minutes a season. A quiet heater is also a longer-lived one, since the same sediment and pressure that cause noise are the things that wear a tank out. If you want a second opinion on a sound you cannot place, the line for plumbing repair is open at any hour.
How noise links to the age of the heater
Sound alone does not mean replacement, but age changes how seriously to take it.
| Heater age | A new noise often means | Reasonable response |
|---|---|---|
| Under 5 years | A one-off cause, a loose part or early sediment | Flush, tighten, monitor |
| 5 to 10 years | Sediment, a worn part or pressure | Flush and have the anode checked |
| 10 years and up | A hardened crust or a worn tank | Get an opinion on repair vs replacement |
Age and noise together are covered in water heater repair vs replacement and how long water heaters last. A noisy tank is a sign, and the next move depends on the rest of the story.
When a noisy water heater needs a plumber
Many sounds can wait a day. These cannot.
Hissing at the base of a gas tank
Water may be reaching the burner. Shut off the gas control and call.
A relief valve spitting steam
Pressure or temperature is too high. Lower the thermostat and call.
Banging with a dripping valve
Pressure may be beyond what the plumbing should see.
Loud popping on an old tank
A heavy crust can hide a worn lining, so get it checked.
Services for a noisy water heater
Each sound points to one of these.
Water heater repair
Elements, burners, valves and controls.
Water heater repair details →Water heater replacement
A worn tank that has run its course.
Water heater replacement details →Tankless water heater
Fans, sensors and descaling.
Tankless water heater details →Low water pressure
When pressure or flow is part of the noise.
Low water pressure details →Questions about why a water heater makes noise
Why is my water heater making noise when it heats?
Is a noisy water heater dangerous?
Why is my water heater popping?
Why does my water heater hiss?
Why does my water heater bang when I turn off a tap?
Can flushing stop the noise?
Why does my electric water heater hum?
Is it normal for a new water heater to make noise?
Why is my tankless water heater loud?
Should I turn off my water heater if it is making a strange noise?
More water heater guides
Noisy water heater? Describe the sound and call
A person answers any hour. Tell them what you hear, when it happens and how old the heater is. Ask about pricing when you call.