Water Heater Making a Popping or Rumbling Noise

Likely causes, most common first

1. Sediment or scale on the bottom of the tank or on electric elements
2. Scale on the heat exchanger of a tankless unit
3. Water hammer from a fast-closing valve or fixture (a bang when water shuts off, not while heating)
4. A relief valve opening because pressure or temperature is too high
5. Loose parts, such as an element or a pipe against a strap

What you can safely check

1. Note when the noise happens: while heating, or when a tap shuts off.
2. Check the thermostat setting. If it is set high, record it and bring it back to a normal setting.
3. Look for water at the relief valve discharge pipe.
4. Make sure the area around the heater is clear.

What not to do

• Do not turn the thermostat up.
• Do not block or cap the relief valve.
• Do not drain a hot tank without letting it cool. The water can scald.
• Do not ignore a noise that comes with a leak or steam.

When to call a professional

Call if the noise is loud or getting worse, you see water or steam at the relief valve, the water is much hotter than normal, or the unit is old. We can flush the tank, replace worn parts, and check the safety valves.

Related service: water heater flushing and maintenance.