Water Heater Making Noise — What Each Sound Means

A noisy water heater is almost always trying to tell you something. The good news: most water heater noises are caused by sediment buildup and can be resolved without replacing the unit — as long as you act before the tank is permanently damaged.

Popping or Rumbling Sounds

This is the most common water heater noise and it's especially prevalent in Los Angeles due to hard water.

Cause: Sediment (calcium and magnesium deposits from hard water) accumulates on the floor of the tank over time. Water trapped beneath the sediment layer boils and pops as it tries to escape through the mineral crust.

What it means: Your tank needs flushing. If the sediment layer is thin, flushing can restore normal operation. If the tank has had years of neglect, the sediment may have hardened and flushing may not fully resolve it — and the sustained overheating can damage the tank lining.

Fix: Annual tank flushing prevents this entirely. We perform tank flushing as a standalone service or as part of our annual maintenance visit.

Hissing or Sizzling

Cause: Hissing usually indicates water is leaking onto a hot surface — either a drip from a valve or fitting landing on the burner assembly, or steam escaping from a small leak.

What to do: Inspect all connections at the top of the tank and around the T&P valve for any drips. If you find a leak, call us — a hissing sound combined with a leak needs prompt attention.

Banging or Knocking (Water Hammer)

Cause: Banging sounds that happen when you turn taps on or off are usually water hammer — a pressure surge in the pipes when water flow is suddenly stopped. This is a plumbing issue rather than a water heater issue, but it's often noticed near the water heater because that's where main supply lines run.

Fix: Water hammer arrestors installed on the supply lines eliminate the banging. We can install these as part of a water heater service call.

Ticking or Tapping

Cause: Ticking or tapping sounds during heating cycles are usually caused by the expansion and contraction of pipes and straps as they heat and cool. This is generally normal, especially in older homes with copper supply lines.

Fix: Loose pipe straps can be tightened. If the sound is coming from inside the tank itself rather than the pipes, have it inspected.

Screeching or High-Pitched Whining

Cause: A screeching sound usually indicates water is being forced through a partially closed valve — either the inlet valve, the T&P valve, or a ball valve somewhere in the supply line. Check that all valves near the water heater are fully open.

Fix: Fully open any partially closed valves. If the screeching persists with all valves open, the T&P valve may be malfunctioning and needs replacement.

Frequently Asked Questions