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: A plumber can check whether the noise is coming from the cylinder, a valve, or surrounding pipework, and tighten or repair any component that is vibrating or loose. Please don’t open, adjust or tighten anything on the cylinder yourself. 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: A plumber can check the valve and 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.
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Related reading
Many cylinder noises come from valves, water pressure, or the surrounding pipework rather than the cylinder itself. A new, loud or persistent noise is still worth having checked before it develops into a bigger issue. See our hot water service, or browse cylinders and prices if yours is already past it. Call 021 837 775.