Water Heater Making Noise: What Each Sound Means

Last updated: April 2026

By the Plumbing Price Guide Team

A water heater making noise is one of the most common plumbing concerns homeowners report, and the sound itself is usually the single most useful clue about what is wrong. Most water heater noises, including popping, crackling, and low rumbling, are caused by sediment buildup and are not dangerous. Some sounds, however, signal a serious problem that requires immediate action. If you are hearing a high-pitched scream, a persistent hiss with visible water, or any sound combined with a gas smell, call a plumber at (641) 637-5215 right now. This guide breaks down every water heater sound you might hear, explains exactly what causes it, walks you through what you can fix yourself, and helps you decide when professional help is needed.

For full repair pricing, see our water heater repair cost guide. If the noise suggests the unit needs replacing, see water heater replacement costs. For general plumber rates, see plumber cost per hour.

What Does Each Water Heater Sound Mean?

Water heaters are not silent appliances. Some operational noise is normal, especially when the burner ignites or an electric element cycles on. But new, loud, or persistent sounds almost always point to a specific problem. The type of sound narrows down the cause, which determines whether you need a $0 DIY fix or a $3,500 replacement.

Popping and Crackling

Popping is the most common water heater noise and the one that brings the most homeowners to this page. It sounds like a coffee percolator, a bowl of rice cereal, or small firecrackers going off inside the tank. The sound is usually loudest when the burner fires or the electric element cycles on, and it may be quiet between heating cycles.

The cause is sediment. Minerals from your water supply, primarily calcium and magnesium, settle to the bottom of the tank over time. When the burner heats the tank bottom, water trapped under the sediment layer turns to steam. Those small steam bubbles push through the sediment and pop as they escape. The thicker the sediment layer, the louder and more frequent the popping.

Popping is not dangerous and not urgent. The water heater will continue to function. However, the sediment reduces heating efficiency, makes the burner or element work harder, and shortens the lifespan of the tank. Flushing the tank is the fix, and it is something most homeowners can do themselves. We cover the full process in the flush instructions below.

Rumbling and Gurgling

Rumbling is essentially the next stage after popping. It means the sediment layer has grown thick enough that the heating process creates a sustained, low-frequency sound rather than individual pops. The tank may sound like a pot of water about to boil or a distant storm. Gurgling, which sounds like water moving through gravel, is a variation of the same problem.

Rumbling indicates a heavier sediment load than popping. The tank is working significantly harder to heat the water. Energy costs are higher. If the rumbling is accompanied by any of the following, the tank may be approaching failure: reduced hot water output (you run out of hot water faster than you used to), rusty or discolored hot water, or water that smells metallic. A rumbling water heater that is less than 8 years old should be flushed as soon as possible. A rumbling water heater that is over 10 years old and has never been flushed may be beyond the point where flushing helps.

Banging and Hammering

A loud banging or hammering sound, often described as the water heater "kicking" or "knocking," is usually not caused by the water heater itself. This is typically water hammer, a pressure shockwave that travels through the pipes when a valve closes suddenly. Washing machines, dishwashers, and quick-closing faucets are common triggers. The sound may seem to come from the water heater because the tank amplifies the vibration.

Thermal expansion is another common cause. When water heats up, it expands. If the plumbing system does not have an expansion tank to absorb that extra volume, the pressure increase can cause pipes to flex against framing, producing a banging or knocking sound. This is more common in homes with a closed plumbing system (a check valve or pressure-reducing valve prevents water from flowing back into the municipal supply).

A water hammer arrestor costs $10 to $30 and can be installed at the appliance that triggers the noise. An expansion tank, installed on the cold water supply line near the water heater, costs $40 to $100 for the part plus $150 to $300 for professional installation. Neither of these problems threatens the water heater itself, but prolonged water hammer can loosen pipe fittings over time.

Hissing and Sizzling

A hissing or sizzling sound from a gas water heater usually means water is contacting a hot surface and immediately evaporating. There are three common causes. The first is a small leak from a fitting, pipe, or the T&P (temperature and pressure) relief valve that drips onto the burner or flue. The second is condensation, which is common when the unit first fires up in cold weather or when cold water enters the tank. Condensation dripping onto the burner is harmless and temporary. The third is a T&P valve that is intermittently releasing small amounts of water due to excessive pressure in the tank.

On an electric water heater, hissing or sizzling typically indicates a leak that is dripping onto a hot element. Electric elements operate at higher surface temperatures than gas burners, so even a small drip creates a noticeable sound.

A hiss combined with visible water or a continuous sound (not just during startup) warrants investigation. Check the T&P valve for discharge, look for dripping connections, and examine the base of the unit for pooling water. If you find a leak, see our water heater leaking guide for next steps.

Screeching and Whistling

A high-pitched screech, whistle, or scream from a water heater demands immediate attention. This sound typically indicates restricted water flow through a partially closed valve or, more seriously, excessive pressure inside the tank. The inlet valve at the top of the water heater is the most common source. If it is partially closed or the washer inside is deteriorating, water forcing through the narrow opening produces a high-pitched sound.

If the screech appears to come from the T&P valve or the tank itself, treat this as a potential safety issue. The T&P valve is designed to open and release water when tank pressure exceeds safe limits (typically 150 PSI or 210 degrees Fahrenheit). A high-pitched sound from this area may mean the valve is attempting to release but is stuck or partially obstructed. Turn off the water heater immediately (gas: dial to OFF; electric: flip the breaker) and call a plumber. Do not attempt to open or test the T&P valve yourself if you hear this sound. For emergency plumber costs, expect $150 to $300 per hour.

Humming

A steady, low hum from an electric water heater is caused by the heating element vibrating as electric current passes through it. The element is a metal rod or loop suspended in water, and the combination of electrical current and water flow can create a vibration that the tank amplifies. This is the least concerning of all water heater noises.

If the humming bothers you, a plumber can slightly tighten the element in its mounting. This costs less than a standard service call in most cases, typically $75 to $150. The humming does not indicate any problem with the water heater and does not affect its performance or lifespan.

Ticking and Tapping

Rhythmic ticking or tapping that starts when the water heater fires up and stops when it shuts off is almost always caused by heat trap nipples. These are small check-valve-like fittings installed on the inlet and outlet pipes of many newer water heaters. They prevent hot water from rising into the cold water supply line through convection. As the temperature changes, the ball or flapper inside the nipple moves slightly, producing a ticking sound.

Thermal expansion of copper or CPVC pipes can also create a ticking or tapping sound as the pipes expand against straps, hangers, or framing when hot water flows through them. This is a pipe issue, not a water heater issue.

Ticking and tapping are normal, harmless sounds. If the noise is bothersome, the heat trap nipples can be replaced with regular dielectric nipples for about $20 in parts. This eliminates the ticking but also removes the small energy-saving benefit the heat traps provide.

Which Sounds Are Urgent and Which Can Wait?

Not every water heater noise requires the same response. Some sounds mean "schedule maintenance when it is convenient." Others mean "turn it off right now." The following table breaks down urgency by sound type so you can decide what to do next.

The general rule: if the noise is accompanied by any other symptom (water on the floor, reduced hot water, discolored water, a gas smell, or visible corrosion), the urgency goes up regardless of the sound type. Multiple symptoms together often indicate a more serious problem than any single symptom alone. For help assessing your situation, see our guide on when to call a plumber.

How Does Sediment Cause Water Heater Noise?

Understanding the sediment process helps explain why flushing works, why the noise gets worse over time, and why some tanks reach a point where flushing can no longer help. Sediment is the single most common cause of water heater noise in tank-style units, accounting for the majority of popping and rumbling sounds homeowners report.

All municipal and well water contains dissolved minerals, primarily calcium carbonate and magnesium. These minerals are not harmful to drink, but they settle out of solution when water is heated. Every time the burner fires or the electric element cycles on, a small amount of mineral sediment drops to the bottom of the tank. Over months and years, this builds into a layer that can reach several inches thick.

In a gas water heater, the burner sits directly below the tank bottom. The sediment layer traps a thin layer of water between itself and the tank floor. When the burner fires, that trapped water superheats and flashes into steam. The steam bubbles push through the sediment and pop as they reach the water above. This is the popping sound. As the sediment thickens, the sound shifts from occasional pops to a sustained rumble because more water is being trapped and more steam is being generated with each heating cycle.

In an electric water heater, the lower heating element may be partially or fully buried in sediment. The element heats the sediment directly, which heats unevenly and causes small steam pockets. The resulting sound is similar but often quieter than in a gas unit because the element does not generate as much concentrated heat as a gas burner.

Homes with hard water, generally defined as water with more than 7 grains per gallon of mineral content, accumulate sediment significantly faster than homes with soft water. A water softener ($1,000 to $3,000 installed) dramatically reduces sediment buildup and extends the life of the water heater. Even without a softener, regular flushing can manage sediment in most situations. In hard water areas, flushing every 6 months instead of annually is recommended.

How to Flush Your Water Heater to Stop the Noise

Flushing a water heater is the most effective way to stop popping and rumbling sounds. It removes the sediment layer that causes the noise. This is a DIY-friendly task that takes 30 to 60 minutes, costs nothing beyond the garden hose you likely already have, and should be performed at least once per year. If you prefer to have a professional handle it, expect to pay $80 to $200 for a standard flush, or include it as part of a plumbing maintenance visit.

Before you begin, gather the following: a garden hose long enough to reach a floor drain or exterior doorway, a flat-head screwdriver (some drain valves require one), and a towel. Wear shoes; the water draining from the tank will be hot.

After the tank reheats, listen for the noise. If the popping or rumbling has stopped or significantly decreased, sediment was the problem and flushing was the fix. Add "flush water heater" to your annual home maintenance schedule. If you live in an area with hard water, consider flushing every 6 months. A water softener can reduce the frequency of required flushing.

When Flushing Will Not Fix the Problem

Flushing is the right solution for most popping and rumbling sounds, but there are situations where it will not help or could actually make things worse. Knowing when flushing is not the answer can save you time and prevent an unexpected problem.

Severe Sediment Buildup

If the water heater has never been flushed and is 5 or more years old, the sediment at the bottom may have hardened into a calcite layer that will not drain through the valve. In this situation, you will open the drain valve and get very little water out, or the water comes out clear because it is sitting above the sediment layer. The hardened sediment remains in the tank. A plumber can sometimes break this up using a descaling solution or by removing the drain valve and inserting a tool, but success is not guaranteed on older units with heavy buildup.

Tank Damage

Sediment that sits against the tank bottom for years traps heat and creates hot spots. These hot spots can weaken the glass lining inside the tank, allowing the steel to contact water directly. Once the steel begins to corrode, the tank is compromised. Flushing removes the sediment but cannot repair the damaged lining. If you notice rusty water after flushing, the lining is likely damaged and the tank will eventually leak. See our guide on what to do when your water heater is leaking.

Sounds Not Caused by Sediment

Flushing addresses popping and rumbling only. It will not fix banging (water hammer), hissing (leaks or T&P valve issues), screeching (pressure or valve problems), or humming (element vibration). If you flush the tank and the noise persists or changes character, the problem is something other than sediment.

Old Units Near End of Life

For a water heater that is over 10 years old, making new noises, and showing other symptoms (reduced hot water, discolored water, visible corrosion), flushing may not be worth the effort. The money spent on a professional flush ($80 to $200) is better applied toward a new unit. See water heater replacement costs to understand your options.

How to Tell If Your Water Heater Is About to Fail

Noise is often the first sign of a water heater approaching the end of its useful life, but it is rarely the only sign. A water heater that is about to fail typically shows multiple symptoms. Recognizing these early gives you time to plan a replacement on your schedule rather than dealing with an emergency failure that leaves you without hot water and potentially with water damage.

Reduced Hot Water Capacity

If you used to get 20 minutes of hot shower water and now you get 10, the effective volume of the tank has decreased. Heavy sediment occupies space in the bottom of the tank, reducing the amount of water available for heating. This is not always a failure indicator on its own (flushing may fix it), but combined with noise and age, it suggests the unit is declining.

Rusty or Discolored Hot Water

Rusty water from only the hot taps (not the cold) indicates corrosion inside the water heater tank. The sacrificial anode rod, a metal rod designed to corrode in place of the tank, has likely been consumed. Once the anode is gone, the tank itself begins to rust. Replacing the anode rod ($150 to $300 professional) can extend tank life if caught early, but if the water is already rusty, internal damage may already be too advanced.

Visible Corrosion or Rust on the Exterior

Rust, flaking metal, or wet spots on the outside of the tank, particularly around seams and fittings, indicate the tank is deteriorating. Exterior corrosion often starts at the bottom where condensation collects and at the top where fittings penetrate the tank.

Multiple Repair Calls in the Past Year

If you have already called a plumber for thermostat issues, element replacement, valve problems, or other repairs within the past 12 months, and the unit is now making noise, the cumulative repair cost may exceed the value of the remaining useful life. The general guideline: if a single repair costs more than 50% of a new unit, or if total repairs in a year approach that threshold, replacement makes more financial sense.

Age Over 10 Years

Most tank water heaters have a useful life of 8 to 12 years. Beyond 10 years, the risk of catastrophic failure (a burst tank flooding your home) increases significantly. An older unit making new noises deserves a professional evaluation, not just a flush. Check your unit's age using our water heater age decoder.

How Much Does It Cost to Fix a Noisy Water Heater?

The cost to resolve a noisy water heater depends entirely on the cause. A sediment flush is one of the cheapest plumbing tasks. A full replacement, triggered when the noise reveals a failing tank, is one of the more expensive ones. The following table breaks down typical costs by problem and fix.

Professional costs include labor, which ranges from $75 to $150 per hour for standard service or $150 to $300 per hour for emergency calls. If the noise is not urgent (popping, rumbling, humming, ticking), scheduling service during regular business hours instead of requesting an emergency visit can cut the total cost significantly.

For a complete breakdown of repair pricing by component, see our water heater repair cost guide. If the diagnosis points toward replacement, see water heater installation costs for a full comparison of tank and tankless options.

Noise in Tankless Water Heaters

Tankless (on-demand) water heaters make different sounds than tank-style units because they operate differently. There is no standing tank of water, so sediment-related popping and rumbling do not apply in the same way. However, tankless units have their own set of sounds that can indicate problems.

Humming or Buzzing (Usually Normal)

A low hum or buzz when the unit is actively heating water is normal for most tankless models. The sound comes from the burner or electric element operating at high output. If the hum is steady and consistent, and the unit is producing hot water normally, no action is needed. A loud or irregular buzz, however, may indicate a loose component inside the unit.

Clicking (Usually Normal)

Clicking sounds when you turn on a hot water tap are the electronic igniter firing in a gas tankless unit. This is normal. You may also hear a click when the unit shuts off after you stop using hot water. If clicking continues without the unit firing (no hot water produced), the igniter may be failing and needs replacement.

Screeching or Loud Whining (Scale Buildup)

A high-pitched screech or whine from a tankless unit almost always indicates scale buildup in the heat exchanger. The heat exchanger has narrow passages that water flows through while being heated. Hard water minerals coat these passages over time, restricting flow. Water forcing through the narrowed passages creates a screeching sound.

The fix is descaling (also called deliming or flushing). A plumber circulates a vinegar or commercial descaling solution through the heat exchanger using a pump. This dissolves the mineral deposits and restores normal flow. Professional descaling costs $150 to $300. Tankless manufacturers recommend descaling annually, or every 6 months in hard water areas. A water softener reduces scale buildup and extends the interval between descaling.

Ignoring scale buildup in a tankless unit does not just cause noise. It reduces efficiency, can trigger error codes that shut the unit down, and eventually damages the heat exchanger. A heat exchanger replacement on a tankless water heater costs $500 to $1,500, far more than annual descaling. Regular maintenance prevents this.

Kettling (Rumbling in a Tankless Unit)

Some tankless units with internal buffer tanks or recirculation systems can develop a rumbling or "kettling" sound similar to a tea kettle about to boil. This is usually caused by restricted flow from scale buildup or an undersized gas line. Descaling is the first step. If the noise persists after descaling, the gas supply pressure should be checked by a plumber. For tankless water heater costs including maintenance and repair, see our dedicated guide.

How Old Is Your Water Heater?

The age of your water heater is one of the most important factors in deciding whether to repair or replace a noisy unit. Most homeowners do not know how old their water heater is, especially if they bought a home with an existing unit. The age is encoded in the serial number on the unit's data plate (usually a sticker or metal plate on the side of the tank near the top).

Each manufacturer uses a different code. Some use the first two digits of the serial number as the year. Others use a letter code where A = January, B = February, and so on. Our water heater age decoder covers the major brands including A.O. Smith, Rheem, Bradford White, and State, with instructions for reading each format.

Age-Based Decision Guide for Noisy Water Heaters

Water heaters that are still under warranty (typically 6 to 12 years for the tank, depending on model) may qualify for a free or discounted replacement if the noise is caused by a manufacturing defect. Check your warranty documentation or contact the manufacturer with your serial number. For sizing a replacement unit, use our water heater sizing calculator.

When to Stop Troubleshooting and Call a Plumber

Many water heater noise issues can be resolved by homeowners, particularly sediment-related sounds that respond to tank flushing. However, there are clear situations where professional help is the right call. The following decision points indicate that it is time to stop troubleshooting and get a plumber involved.

Call Immediately If:

• You smell gas near the water heater (leave the house first, then call)
• The water heater is making a high-pitched scream or whistle (turn it off, then call)
• You see water spraying from the tank or fittings
• The T&P valve is continuously discharging water
• There are scorch marks or signs of fire near the burner

Schedule a Plumber Soon If:

• Flushing did not stop or reduce the popping or rumbling sound
• The noise is accompanied by rusty water or reduced hot water output
• The water heater is over 10 years old and making any new sound
• You hear hissing but cannot identify the source
• The drain valve is clogged and you cannot complete a flush
• You attempted a flush and the water draining was heavily discolored or contained large sediment chunks
• The unit has not had an annual maintenance check in several years

DIY Is Fine If:

• The sound is popping or crackling and the unit is under 8 years old (flush it)
• The sound is humming from an electric unit (tighten the element or ignore it)
• The sound is ticking and comes from the pipes, not the tank (heat trap nipples)
• The sound is banging that correlates with appliances turning on or off (water hammer arrestor)

If you are unsure which category your situation falls into, err on the side of calling a professional. A standard diagnostic visit costs $75 to $150, which is far less than the cost of water damage from a failed tank or the risk of a gas-related safety issue. If you do not have hot water at all, see our guide on no hot water this morning for step-by-step troubleshooting.

Frequently Asked Questions