You are sitting quietly in your living room, perhaps reading or watching TV, when you hear it coming from the utility closet or basement: Click… tick… click-click… tick.

Few household sounds are as unsettling as an unexplained noise coming from a major appliance—especially one that holds dozens of gallons of scalding water and uses high-voltage electricity or combustible gas.

If you find yourself Googling, "Why does my water heater make clicking noise?" you are likely worried about three things: Is it dangerous? Is it about to break? And how much will it cost to fix?

The good news is that not every click is a catastrophe. The bad news is that some clicks are definite warning signs that your unit needs maintenance before a minor annoyance becomes a major flood or safety hazard.

At TruePlumber, we believe an informed homeowner is a safer homeowner. Here is a diagnostic guide to the five most common reasons your water heater is acting noisily, and what you should do about it.

🚧 Important Safety Warning Before You Begin 🚧

If you have a gas water heater and the clicking is accompanied by the smell of gas (sulfur or rotten eggs), leave the house immediately and call your utility company or 911 from a safe distance.

If the noise is definitely just a noise, read on to diagnose the issue.

Cause #1: Sediment Buildup (The "Trapped Steam" Click)

Applicable to: Gas and Electric Water Heaters

This is the most common cause of unusual noises in water heaters, particularly in areas with hard water.

Over time, minerals like calcium and magnesium dissolved in your water supply precipitate out of the water as it heats up. These minerals settle at the bottom of the tank, forming a layer of sand-like sediment or hardened lime scale.

Why it makes a clicking noise: Water gets trapped underneath this layer of sediment right against the burner (gas) or the lower heating element (electric). As that trapped water turns to steam, it creates small bubbles that burst forcefully against the sediment layer. While often described as "popping" or "rumbling," smaller steam bursts frequently sound like sharp, repetitive clicking or ticking.

The Fix: The tank needs to be flushed to remove the sediment. This is an essential annual maintenance task. While a handy homeowner can attempt a DIY flush, severe buildup may require professional cleaning.

Related: Learn more about the signs that you need a new unit in our Guide to Water Heater Repair vs. Replace Decisions.

Cause #2: Thermal Expansion (The "Ticking Pipes" Noise)

Applicable to: Gas and Electric Water Heaters

Sometimes, the noise isn't coming from inside the tank at all—it’s coming from the pipes attached to it.

Why it makes a clicking noise: Basic physics dictates that metal expands when heated and contracts when cooled. When your water heater fires up and sends hot water into your home's copper piping, those pipes expand slightly. If the pipes are running through tight wooden framing holes or are strapped tightly against a wall, the friction of the metal moving against wood or metal straps creates a rhythmic ticking or clicking sound.

The Fix: This is generally harmless and considered a normal operational noise. However, if the noise is new and very loud, it could indicate high water pressure. A plumber can install a thermal expansion tank or adjust pipe straps to mitigate the noise.

Cause #3: Gas Ignition Failure (The "Trying to Light" Click)

Applicable to: Gas Water Heaters Only

If you have a gas unit, a repetitive, rhythmic clicking sound that happens when the unit is trying to heat up—similar to the sound of trying to light a gas stovetop burner—indicates an ignition issue.

Why it makes a clicking noise: Modern gas water heaters use an electronic ignition spark rather than a standing pilot light. The clicking is the igniter sparking, trying to light the gas burner. If you hear the clicking continue for several seconds but don't hear the "whoosh" of the burner lighting, the system is failing to ignite.

This is usually caused by:

A faulty spark igniter.
A dirty or broken thermocouple (the safety sensor that detects flame).
Issues with the gas control valve.

The Fix: This requires a professional. Working on gas control valves and ignition systems can be dangerous if not done correctly. You need a licensed technician to diagnose why the burner isn't catching the spark.

For more on gas appliance safety, visit the U.S. Consumer Product Safety Commission (CPSC).

Cause #4: Loose Heating Elements

Applicable to: Electric Water Heaters Only

Electric water heaters use large metal immersion elements protruding into the tank to heat the water.

Why it makes a clicking noise: If an element has worked itself slightly loose over time due to thermal cycling, it may gently rattle or click against the side of the tank as the water circulates around it. Furthermore, heavy lime scale buildup on the element itself can cause ticking sounds as the element heats up and expands against the mineral crust.

The Fix: A professional plumber should test the elements. They can tighten loose elements or, more likely, replace elements that are heavily corroded or scaled up.

Cause #5: Heat Trap Nipples

Applicable to: Newer Gas and Electric Water Heaters

Modern, energy-efficient water heaters are often installed with "heat trap nipples" on the cold water inlet and hot water outlet pipes on top of the tank. These contain small metal balls that allow water to flow only one way, preventing heat from escaping up the pipes when the water isn't running.

Why it makes a clicking noise: Sometimes, these small metal balls inside the nipple rattle or click as water flows past them. This is a harmless operational noise.

The Fix: If the noise is unbearable, a plumber can replace them with non-heat-trap dielectric nipples, though you may lose a small amount of energy efficiency.

Summary: When to Call a Pro

Never ignore a new noise from your water heater. It is your home telling you something needs attention.

Ignore it if: It's a gentle ticking sound from pipes expanding (thermal expansion) that you've heard for years. Monitor it if: It's a slight clicking likely caused by heat traps. Act now if: The clicking is loud, accompanied by rumbling (sediment), or sounds like a gas burner failing to light.

Trying to DIY repairs on gas lines or high-voltage electrical connections is risky. When in doubt, bring in a vetted expert to ensure your hot water is safe and reliable.

Don't guess when it comes to your water heater. Enter your zip code below to connect instantly with licensed, pre-vetted local plumbers ready to diagnose that clicking noise today.

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