Why Is My Water Heater Making Strange Noises?

Your water heater should operate relatively quietly. A gentle hum from an electric unit or the soft whoosh of a gas burner is normal. However, if your water heater starts sounding like a percolating coffee pot or a small jet engine, it is trying to tell you something is wrong.

Ignoring strange noises can lead to serious damage, leaks, or total failure. Here is a guide to decoding the most common water heater sounds and what you should do about them.

1. Popping, Rumbling, or Banging

This is by far the most common noise complaint homeowners have. It often sounds like rocks tumbling around inside the tank or loud popcorn popping.

The Cause: Sediment Buildup. Over time, minerals present in the water (calcium and magnesium) settle at the bottom of the tank. The heat from the burner bakes this sediment into a hard, crusty layer. Water gets trapped under this layer, and when it is heated, it boils, turns to steam, and bursts through the sediment crust, creating that popping or rumbling noise.

The Fix: The tank needs to be flushed by a professional. If the sediment has hardened too much, flushing might not work, and the water heater may need to be replaced, as this buildup severely weakens the tank and causes it to crack.

2. High-Pitched Whistling or Screeching

A screeching noise can be alarming, but the cause is usually related to water flow rather than the tank itself.

The Cause: Pressure or Valves. This sound is typically caused by water being forced through a small opening. It could be a partially closed shut-off valve, a worn-out check valve, or a malfunctioning Temperature and Pressure (T&P) relief valve. If the T&P valve is whistling, it means it is struggling to release excess pressure—a dangerous situation.

The Fix: Check to ensure the main water valves are fully open. If the sound persists, call a plumber immediately to inspect the T&P valve.

3. Sizzling or Hissing

If you hear a noise that sounds like bacon frying or water hitting a hot pan, pay attention.

The Cause: Condensation or a Small Leak. In gas water heaters, condensation can form on the outside of the tank and drip down onto the hot burner, creating a sizzle. This is normal. However, if the hissing is constant, you might have a pinhole leak in the tank that is dripping water onto the hot burner.

The Fix: Inspect the area under the tank for standing water. If you suspect a leak, turn off the water and gas/power, and call a professional immediately.

4. Ticking or Tapping

A rhythmic ticking sound is usually less concerning than the others.

The Cause: Pipe Expansion. As hot water flows through your home's copper or PVC pipes, the pipes expand. If they are strapped tightly to the wooden joists in your walls or floors, they can rub against the wood, creating a ticking or tapping sound. In electric heaters, the heating elements can also make a slight clicking noise as they turn on and off.

The Fix: Usually, no fix is required unless the noise is extremely disruptive, in which case a plumber can adjust the pipe straps.