What That Noise from Your Water Heater Really Means

Water heater (aka hot water cylinder) has a heavy workload, so it’s important to keep an eye (or ear) on how it’s performing. Some sounds are normal — but humming, knocking, screeching, or tapping? Those need attention.

1. Humming

A humming water heater can be more than just annoying — it could mean internal parts are loose. The humming usually comes from vibrations inside the tank.

How to fix: Turn the unit off and carefully inspect and tighten components to stop the vibration. Be extremely cautious — the water inside is dangerously hot.

2. Knocking or Hammering

That banging noise you hear? It’s likely “water hammering” — when flowing water crashes into a valve too fast. It’s loud, but typically not dangerous.

3. Screaming or Screeching

Hearing a high-pitched squeal from your water heater? The check valve might be partially closed, forcing water to squeeze through and whistle.

How to fix: Make sure the check valve is fully opened. A professional plumber can easily sort this out.

4. Tapping

Tapping sounds often mean sediment buildup or issues with check valves. Left untreated, it can lead to damage inside the heater.

How to fix: A plumber should inspect the heating element, valve, and possibly drain the tank to remove sediment safely.