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Your water heater quietly labors away each day, providing hot water on demand. But when it starts making unexpected noises, it can be a cause for concern. Is it normal? Is something wrong? This guide will help you decipher the symphony (or cacophony) coming from your water heater, so you can determine what’s routine and what requires professional attention.

1. Popping or Cracking Noises

What’s Normal: A mild popping or crackling sound is common, especially in older tank-style heaters. This is often due to sediment build-up at the bottom of the tank. As the heater operates, water gets trapped under the sediment, and as it heats up, steam bubbles form and pop.

What’s Not: If the popping sound is extremely loud or occurs even after a recent flushing of the tank, it may suggest excessive sediment build-up, requiring a more thorough cleaning or even a potential issue with the heating element.

2. Ticking or Tapping Sounds

What’s Normal: Some heaters have check valves or heat traps that prevent backflow of water. These can make ticking or tapping sounds as water flows, and it’s typically not a cause for concern.

What’s Not: If the ticking becomes persistent or changes in its pattern, it’s worth investigating further. It might be a sign of a problem with the valve itself.

3. Rumbling or Roaring

What’s Normal: A slight rumble as the water heats is common, especially if there’s some sediment in the tank.

What’s Not: A loud roaring noise is not standard. It could mean there’s a significant amount of sediment, causing overheating. This can reduce your heater’s lifespan and efficiency. If you hear a roaring sound, consider draining and cleaning the tank.

4. Whining or Screeching

What’s Normal: Some high-efficiency tankless heaters might produce a mild whine as they operate, but it shouldn’t be overly loud.

What’s Not: A sharp screeching or high-pitched whining sound from any heater is a red flag. This noise can be indicative of a malfunctioning pressure relief valve or issues with the heating element.

5. Hissing Sounds

What’s Normal: A gentle hissing noise can sometimes be heard in tankless heaters due to the rapid heating of water.

What’s Not: In a tanked heater, persistent hissing may suggest a leak, where water is dripping onto the burner. If left unchecked, this could lead to more significant problems.

6. Sizzling Noises

What’s Normal: Unfortunately, nothing. A sizzling sound is not standard for any water heater.

What’s Not: Sizzling typically points to a leak, where water is contacting hot surfaces within the heater. Address this promptly to avoid further complications.

7. Banging or Knocking

What’s Normal: Some noise can occur when the heater turns off, and metal parts contract. A single knock or two isn’t typically concerning.

What’s Not: Persistent knocking or banging noises might indicate a problem with the expansion tank or even ‘water hammer’ – a phenomenon where fast-closing valves cause water to slam against the pipes. It’s best to consult with a professional if these noises are frequent.

8. Gurgling or Boiling Sounds

What’s Normal: Mild gurgling can be a result of air bubbles in the system, especially after maintenance or installation.

What’s Not: If your heater sounds like it’s boiling, it’s a severe issue. It suggests the unit is overheating, potentially because of malfunctioning thermostats or excessive sediment. This can be dangerous, and you should shut off the heater and seek professional assistance.


While some noises from your water heater can be deemed as “business as usual,” others are indicators of underlying issues that can impact efficiency, safety, and longevity. By familiarizing yourself with these sounds, you can ensure that your water heater gets the attention it needs before minor issues evolve into more significant problems.

Remember, regular maintenance, including flushing sediment from tanked heaters, can prevent many common issues. And if you’re ever unsure about a sound or its cause, it’s always best to err on the side of caution and consult with a seasoned professional. After all, a little proactive care can ensure that your water heater provides warm, comforting showers for years to come.