Water heater popping or rumbling

Popping or rumbling from a tank-style water heater is most often sediment at the bottom of the tank, but a few other sounds mean something different and a couple need action right away. Let's sort out what you are hearing. This page is about tank heaters; for a tankless unit, A. O. Smith points owners to its tankless support resources or a rep.

Also searched as: water heater popping sound, water heater popping noise, water heater rumbling, water heater rumbling noise.

Before you start. If you smell gas, or hear hissing near a gas line or the burner, leave and call 911 and your gas utility from outside. If water or steam comes out of the relief valve pipe, keep away from the end of the pipe and call a licensed plumber right away. Never cap, plug or block the relief valve or its pipe.

Every question and answer on this page, in order

Question 1: Do you smell gas, or hear hissing near a gas line or the burner area?

Atmos Energy says to use sight and hearing too, not smell alone. If you are not sure, choose the first answer.

Yes, or I'm not sure: Leave now: possible gas leak
No: go to question 2

Question 2: Look from a distance with a flashlight. Do you see water or steam where it should not be?

The relief valve is the lever valve near the top or side of the heater, with a pipe running down toward the floor. Do not touch it or the hot tank, and do not step into standing water.

Water or steam is coming out of the relief valve pipe: Call a plumber now: the relief valve is discharging
Water is leaking from the tank or its fittings, or there is a puddle under the heater: Call a plumber: hissing, sizzling or a leak
No water or steam anywhere it should not be: go to question 3

Question 3: What does the sound do?

Think about when you hear it: while the water is heating, when a tap shuts off, or all the time.

Popping, rumbling or crackling while the heater is heating water, often after hot water was used: Call a plumber: likely sediment in the tank
Hissing, sizzling or spitting, like water on a hot pan: Call a plumber: hissing, sizzling or a leak
Knocking or banging right when a tap or appliance shuts off: Call a plumber: knocking is likely water hammer
Quiet ticking, clicking or gurgling, a soft hum on an electric heater, or a soft ignition sound on a gas heater, brief and regular: Probably normal: quiet heater sounds
Whistling, screeching, a loud hum, or something else I cannot place: Call a plumber: whistling, screeching or another odd sound

Possible results

Need the words for the phone call? Build a what-to-tell-the-plumber checklist, or read when to call a plumber.