Most water heater noises are normal or minor. Ticking is pipes and heat traps expanding; a brief sizzle on a gas tank is condensation hitting the burner; humming is an element or a heat pump's compressor and fan; clicking is ignition or relays. Whistling, screaming, steady hissing and loud knocking deserve a check: a partly closed valve, a relief valve releasing, a leak, or water hammer.
- Pin down when the noise happens (while heating, while water runs, when a tap closes, or at rest) before deciding what it means.
- Ticking, a short sizzle after a big draw, a steady hum and a click or two at start-up are usually normal.
- A whistle or scream at the tank points to a restricted valve or, more seriously, a relief valve releasing; check the discharge pipe first.
- Knocking when a tap or appliance valve shuts is water hammer, a plumbing pressure problem fixed at the valve, not at the heater.
- A hiss with a gas smell, steam from the relief pipe, or sizzling where water meets wiring means stop and call.
01 /Is a hot water heater supposed to make noise?
Yes, a working water heater makes some noise, and each type has its own normal sounds. The trick is telling a healthy sound from a symptom, and the most useful clue is timing: what was happening when you heard it.
| Heater | Normal sounds |
|---|---|
| Atmospheric gas tank | A soft whoosh as the burner lights, a low roar while it runs, occasional ticks as the flue and pipes warm |
| Power vent | A steady fan whir before, during and just after each burn; a click as the pressure switch closes |
| Electric tank | Near silence, sometimes a faint hum or a click as a thermostat switches |
| Heat pump | A fan and compressor hum through long heating cycles, much like a dehumidifier |
| Tankless | A fan, a click or two and the burner roar whenever hot water runs |
Then narrow it down with four questions. Does it happen while the heater is heating, only while water is running, at the moment a tap or appliance shuts off, or at rest? Heating noises come from the burner, elements, sediment or expanding metal. Running-water noises come from valves and pipes. Shut-off noises are water hammer. Noises at rest are usually pipes cooling, a relief valve seeping, or a control reporting a fault.
Rumbling, popping and a kettle-like crackle while a gas burner runs are sediment on the tank bottom. That has its own guide, rumbling and popping water heater, so this page covers the other sounds.
02 /What does each water heater noise mean?
Match the sound, then do the safe check before deciding whether to call anyone.
| Noise | Likely cause | Safe check | When to call |
|---|---|---|---|
| Ticking or tapping at the top pipes during and after heating | Pipes and heat-trap fittings expanding and contracting | See whether it follows heating cycles; look for pipes rubbing on straps | Only if it comes with a leak |
| Ticking in walls or ceilings as hot water runs | Copper lines sliding against wood or straps as they warm | Listen along the pipe run | A plumber can add cushioned supports if it bothers you |
| Brief sizzle at a gas burner after a big draw | Condensation dripping onto the burner | It should fade as the tank warms | If it persists every cycle or the flame looks disturbed |
| Sizzling from an electric tank while heating | Scale on the elements | Flush the tank | If flushing does not help, the elements may need replacing |
| Sizzle or crackle at an element panel, with dampness | A leak at the element gasket reaching live terminals | Switch the breaker off; do not open the panel with power on | Now |
| Steady hiss at the T&P valve or its pipe | Valve seeping or releasing | Look for water or warmth at the pipe outlet | Soon for a drip; now for steam or a rush of hot water |
| Hiss near the gas line or control | Possible gas leak | Do not investigate | Leave and call from outside |
| Whistle while hot water runs | Partly closed or failing valve, or a restriction in a fitting | Open the heater's cold supply valve fully | If it persists, a plumber replaces the valve |
| Screaming or roaring from the discharge pipe | T&P valve opening on high temperature or pressure | Keep clear; turn off the heat from a safe spot | Now |
| High whine from a power vent's blower | Worn fan bearing | Note whether it gets louder over weeks | Before the fan seizes |
| Hum from an electric tank | Element vibration or a loose element | Usually harmless; look for dampness at the panels with power off | If it buzzes loudly or comes with a leak |
| Hum and fan noise from a heat pump | Normal compressor and fan operation | Clean the filter; check the feet, level and panel screws | If it rattles, grinds or runs non-stop without heating |
| Bang or knock when a tap or appliance shuts | Water hammer | Note which fixture triggers it; measure house pressure | A plumber for arrestors, pressure control or pipe supports |
| Rapid clicking with no ignition | Igniter or control retrying | Read the status light or code | If it locks out after a reset |
03 /What causes ticking and tapping?
Ticking is metal expanding and contracting. Copper and steel pipes lengthen slightly as hot water flows through them, and wherever they are strapped tight or pass through a joist, they catch and release with small ticks. The flue inside a gas tank does the same as it heats and cools.
Heat traps are another common source. Natural Resources Canada's water heater guide explains that heat traps stop unwanted convective circulation of water within the pipes, which saves standby energy. Some designs use a small ball or flap in the fitting, which can tap as flow starts and stops or as the water warms. The noise is harmless. If it drives you mad, a plumber can swap the fittings for a quieter style or a looped pipe, but do not remove heat traps without replacing them with something that does the same job.
04 /Why does my water heater hiss or sizzle?
Hissing and sizzling usually mean water is landing on something hot or something is escaping under pressure, and the source decides whether it matters.
- Condensation on a gas burner. After a big draw of cold water, exhaust vapour condenses on the cold tank and drips onto the burner, sizzling until the tank warms. Heavy, persistent dripping deserves a technician's look.
- A seeping T&P valve. A soft hiss at the top or side of the tank, with water at the end of the discharge pipe, means the relief valve is releasing. Find out why in T&P valve dripping.
- Water on an element. Sizzling from inside an electric tank is usually scale on the elements, which a flush helps. Sizzling behind an element access panel, with dampness or rust streaks, means a gasket leak is reaching live parts. Switch the breaker off before anything else.
- A leak above a hot surface. A fitting dripping onto the flue or burner sizzles; hot water tank leaking shows how to trace it.
- Gas. British Columbia's natural gas safety brochure notes that a hissing sound can signal escaping gas, just like the rotten-egg smell. A hiss near the gas line or control is a leave-first situation.
05 /What makes a water heater whistle or scream?
A whistle means water or steam is being forced through a narrow opening. The most common cause is harmless; the least common is urgent.
A partly closed valve is the usual culprit. If the cold supply valve above the tank was not fully reopened after maintenance, or an old gate valve has lost part of its gate, water squeezes past and whistles whenever hot water runs. Open the valve fully and listen again; a valve that still sings needs replacing. A worn pressure-reducing valve can whistle too; the City of Calgary notes that homes built after 1990 in areas over 80 psi have one, and that one over five years old may need servicing.
A relief valve releasing is the urgent case. A scream, roar or rush from the discharge pipe means the T&P valve has opened on high temperature or pressure. Keep clear of the pipe, turn off the gas control or breaker if you can reach it safely, and call. Can a water heater explode? explains why a relief valve doing this is working, and what happens when one cannot.
A high-pitched whine from the top of a power vent is different: it is usually the blower's bearings wearing, which power vent troubleshooting covers.
06 /Why is my water heater humming?
Humming is usually electrical or mechanical and normal. Electric elements can vibrate slightly in the water as they heat, and a hum that has always been there is nothing to fix. A new, louder buzz from an element can mean it has loosened in its fitting; with the breaker off, look at the panel for dampness, and have a plumber or electrician tighten or replace the element.
Heat pump water heaters hum by design. A fan pulls room air across the evaporator and a compressor moves the heat into the tank, and both run through long, gentle heating cycles. Natural Resources Canada's guide notes these heaters remove heat and humidity from the air around them, which is why they sound and feel like a dehumidifier. A clogged filter makes the fan louder, and an unlevel unit or loose panel adds rattles. Keep them away from bedrooms; heat pump water heaters covers placement.
07 /What causes knocking or banging pipes near the water heater?
Knocking or banging when a tap, toilet, washing machine or dishwasher shuts off is water hammer. Moving water stopped suddenly by a fast-closing valve sends a pressure spike back through the pipes, and loose pipes jump and bang against the framing. It is loudest with high house pressure and quick-closing solenoid valves.
- Find the trigger. Note which fixture or appliance causes it; the fix goes there.
- Measure the pressure. A gauge on a hose bib tells you whether pressure is high enough to make hammer worse.
- Fix at the source. A plumber can fit water hammer arrestors at the offending valve, service or add a pressure-reducing valve, and secure loose pipe runs.
Where expansion tanks fit in: a closed system, one with a pressure-reducing valve, check valve or backflow preventer, lets pressure climb every time the tank heats, which stresses fittings and can make hammer and relief-valve drips worse. An expansion tank absorbs that thermal expansion. It is sized for heating, not for hammer, so it complements an arrestor rather than replacing one.
Knocking from inside the tank while the burner runs is a different sound with a different cause: sediment, covered in the rumbling guide.
08 /Why does my water heater click?
Clicking is usually a control doing its job. The gas valve clicks as it opens and closes, electric thermostats snap as they switch, relays on a control board click, a heat pump's contactor clicks as the compressor starts, and a spark igniter ticks rapidly for a few seconds on power vents and tankless units.
Two patterns deserve attention. Rapid clicking that repeats without the burner lighting means ignition is failing and the control is retrying; read the code and see power vent troubleshooting or no hot water. Frequent on-off clicking with short burns can mean the thermostat or control is cycling too often, which a technician should check. If a noise does not fit anything here, the Water Heater Troubleshooter ranks causes by symptom, and you can request quotes for a service visit.
FAQQuestions people ask
Is a hot water heater supposed to make noise?
Some noise is normal: the burner's whoosh and roar, a power vent's fan, a heat pump's hum, and ticks as pipes warm. Whistling, screaming, steady hissing, loud knocking, or rumbling from sediment are signs to check something.
Why is my hot water tank making noise when no water is running?
A tank reheats on its own as it loses heat, so burner or element sounds can start at any time. Ticking as pipes cool is normal. A hiss at rest often means the relief valve is seeping; check the end of its discharge pipe.
Does a hot water tank make noise when heating?
Yes. Gas tanks whoosh and roar softly, and the flue and pipes tick as they warm. Electric tanks are nearly silent. Loud popping or rumbling while heating means sediment and a flush is due.
How loud should a power vent water heater be?
A steady fan whir while it runs is normal, and the termination outside can be audible. A whine, grinding or rattling that develops over time usually means worn blower bearings and needs a technician.
Why does my water heater whistle?
Usually a partly closed or failing valve on the supply, so open the cold supply valve fully. A scream or roar from the relief valve's discharge pipe is different and urgent: turn off the heat from a safe spot and call.
Can water hammer damage a water heater?
Repeated pressure spikes stress fittings, valves and connections throughout the plumbing, including at the heater. Fix hammer at the valve that causes it with arrestors or pressure control rather than living with the banging.