In this article
A water heater that pops, rumbles or bangs is telling you something about what is happening inside the tank. Most of the time the cause is sediment, and most of the time it can be dealt with before it turns into a leak. Here is what each sound usually means.
Popping or rumbling: sediment in the tank
Minerals in the water settle to the bottom of the tank over the years and form a layer of sediment. On a gas water heater the burner sits under that layer. Water trapped beneath the sediment boils, and the steam bubbles force their way up through it. That is the popping sound. A heavy layer makes a deeper rumble.
The noise itself is not dangerous, but the sediment is doing damage. It makes the burner run longer to heat the same water, it overheats the bottom of the tank, and it shortens the life of the heater.
Crackling or sizzling
On a gas heater, light crackling can be condensation dripping onto the burner, which is common when the tank is refilling with cold water. On an electric heater, a hiss or sizzle usually means the lower heating element is buried in sediment. Sizzling together with water on the floor means a leak is dripping onto something hot, and that needs attention the same day.
Banging or knocking when a tap shuts off
If the bang comes from the pipes, at the moment a faucet or the washing machine shuts off, it is water hammer and not the heater itself. A fast-closing valve sends a pressure shock through the line. It is worth fixing, because repeated shocks loosen joints.
Ticking
A steady tick as the heater warms up or cools down is usually the pipes or the heat-trap fittings expanding. It is normal.
Screeching or whistling
A high-pitched sound means water is being forced through a restriction. Check that the cold-water valve above the heater is fully open. If the sound comes from the temperature and pressure relief valve on the side of the tank, turn the heater off and call a plumber. That valve is the tank’s safety device.
What you can do: flush the tank
Draining a few gallons from the valve at the bottom of the tank once a year carries sediment out before it hardens. On a heater that has never been flushed and is more than ten years old, be cautious. The sediment may have hardened into a crust that will not drain, and an old drain valve may not close properly again. That is a good job to hand to a plumber.
When noise means the heater is near the end
Call a plumber if the noise comes with any of these:
- Rusty or brown hot water
- Water around the base of the tank
- Hot water that runs out much sooner than it used to
- A heater that is more than ten to twelve years old
Common questions
Is a popping water heater dangerous?
Not usually. It is a sign of sediment, which wears the tank out faster. The exception is a relief valve that is hissing or discharging, which should be checked right away.
Will flushing stop the noise?
Often, if the sediment is still loose. On an older tank the noise may come back or may not change at all, which usually means replacement is not far off.
We repair and replace tank and tankless units across Macomb County. See our water heater service, read tankless vs. traditional water heaters, or call (586) 943-4158.
