Why Does My Water Heater Pop or Rumble?

If your tank water heater has started popping or rumbling, the cause is almost always sediment. Minerals from untreated water settle inside the tank and build up over time, and that buildup is what makes the noise.

The sound itself isn't the emergency. What matters is what it tells you about the tank, and whether a flush can still bring it back.

What causes a water heater to pop or rumble?

Sediment buildup inside the tank. When a home runs on water that isn't softened or filtered, sediment collects inside the water heater over time. That buildup is what produces the popping and the low rumble.

Is a rumbling water heater dangerous?

Not usually. The noise is more of a nuisance than a hazard. The real concern is what it signals: a heater that rumbles loudly may have more sediment in it than a flush can remove, which means it may be past the point of saving.

Can flushing the tank stop the noise?

Sometimes, but a loud rumble lowers the odds. The sediment in a noisy tank isn't loose silt. It has hardened and clumped together, so it won't wash out through the small drain port at the bottom of the heater the way a routine flush expects it to.

For tanks like that, we use a combination of air and pumping to break the hardened sediment apart so it can come out. We recommend trying that before you replace the heater, because when it works, it saves you the cost of a new unit. When it doesn't, replacing the heater is the better use of your money.

How often to flush a healthy tank, and how we do it, is covered on our water heater repair and replacement page.

What does a water heater flush cost?

A typical flush runs $125 to $250. On a noisy tank, think of it as the first step: if the air and pumping method breaks up the sediment, the flush may be all you need.

When does the noise mean it's time for a new water heater?

When the sediment won't break up and come out. At that point, the tank has done what it can, and a new heater is usually the smarter spend.

A standard 40 to 50 gallon tank replacement runs $2,100 to $2,800, and a 70 to 75 gallon tank runs $3,000 to $5,000. What moves the price, and how we decide between repairing and replacing, is laid out on our water heater page.

Could the noise be something other than sediment?

In our experience, a rumble or a pop from a tank water heater comes back to sediment. A vibration from the burner assembly is a different problem, though the two can be hard to tell apart by ear.

That difference matters. If the sound is coming from the burner assembly, there could be a problem with the gas supply. So whatever you think the noise is, have a plumber come out and look at it rather than waiting it out.

Why do Ontario water heaters build up so much sediment?

Because Ontario's water is very hard, with a lot of calcium buildup, and untreated, unsoftened water is exactly what leaves sediment in a tank. The same hard water wears out the cartridges in faucets and shower valves, sometimes within a few years when the water isn't treated. We cover what else we see in local homes on our Ontario plumbing page.

Softened water means less sediment settling in the tank in the first place. If your heater is new, or you've just had a noisy one flushed or replaced, a water softener helps keep the sediment from building back up.

What should you do if your water heater is rumbling?

Call a plumber and have it looked at. If it's sediment, we'll try the air and pump method first and tell you honestly whether the tank can be saved. If it's the burner, it may be a gas issue that shouldn't wait. Call (909) 600-4561.