Water heaters are usually silent, so a new noise gets noticed. Each sound has a likely cause, and most of them are dealt with by the same twenty-minute flush. A few mean something more.
Rumbling, popping or banging
The most common, and the one that worries people most. Sediment has built up on the bottom of the tank, and water trapped under it boils and bursts through with a pop. On a gas heater it can sound like a kettle, or like someone dropping marbles.
It does no immediate harm, but the sediment layer makes the burner work harder, overheats the tank bottom, and shortens the heater's life. Flush the tank. If the noise continues after a flush, the sediment may have hardened into a crust that will not drain, and the heater is living on borrowed time. Bergen County's moderately hard water makes this the rule rather than the exception on a heater that has never been flushed.
Sizzling or hissing
On a gas heater: water dripping onto the burner. Either condensation, which is normal on a cold refill and stops after a few minutes, or a leak from somewhere above the burner, which is not. Look for the source. Water from a fitting at the top can be fixed; water from the tank itself cannot.
On an electric heater: sediment on the heating element, or an element that is failing. Flush the tank. If the noise continues and the hot water is lukewarm, an element needs replacing.
Ticking or tapping
Pipes expanding and contracting as they heat and cool, and rubbing where they pass through a joist or a strap. Harmless. A little foam insulation or a loosened strap at the spot stops it. Some heaters also have heat-trap nipples at the top, with small flaps that tick as water flows. Also harmless.
A high whine or squeal
Water forcing through a narrow opening. Check that the cold water valve on top of the heater is fully open; a valve that is nearly closed whistles. A clogged inlet on an old heater does the same. A whine from the burner of a gas heater can mean the gas pressure or the burner needs adjusting, which is a plumber's job.
Crackling on a gas heater
Sediment, again, or the burner assembly needing cleaning. A yearly service on a gas heater includes cleaning the burner and checking the flame, which should be steady and blue.
Knocking when a tap closes
That is water hammer in the pipes, not the heater. It is caused by fast-closing valves on appliances, and it is fixed with an arrestor on the offending line.
Sounds that mean turn it off
- A rumble that builds, with the relief valve discharging or steam at a tap: the thermostat has failed and the tank is overheating. Turn the heater off and call a plumber.
- A whoosh or a bang when the burner lights on a gas heater: delayed ignition, which can be dangerous. Turn the gas control to Off and call a plumber.
- Any noise together with a smell of gas: leave the house and call PSE&G or 911 from outside.
The habit that prevents most of it
Flush the tank once a year. Twenty minutes, a garden hose, and a heater that runs quietly and lasts longer.
When to call a plumber
- Rumbling that continues after a flush
- A failing element or thermocouple
- Any sign of overheating or delayed ignition
- Water from the tank itself
Find a licensed plumber near your town.