Hot water tanks are conveniences many of us take for granted and wouldn’t want to be without, but a water heater making noise can make you second guess that convenience. Whether electric, gas, powered by another source, or tankless, a humming, banging, vibrating, hissing, or screeching that emanates from a hot water heater can be disturbing, and cause for concern.
A noisy hot water heater is often the result of sediment or mineral build-up, water pressure changes, restricted water flow, leaks, condensation, anode rod, or heating element. Periodic maintenance commonly prevents most problems, but a plumber may be required for some issues.
In this guide, we’ll identify different noises a hot water tank or tankless water heater may make, potential causes, and how to fix the noise problems. We also offer some maintenance tips and suggestions. Hopefully, we will provide you with a solution to your water heater noise problem and save you the cost of a visit from a plumber.
Contents (Jump to Topic)
- Should Water Heaters Make Noise?
- Is a Noisy Water Heater Dangerous?
- Common Water Heater Noises: Causes and Fixes
- Tankless Water Heater Noises
- Water Heater Maintenance Tips
Should Water Heaters Make Noise?
Water heaters commonly make some noise as water flows in and out and cold water is heated. Depending on the type of heat source or system, there may be other associated noise as relays click or meters whir. It is the unusual noises that often indicate there is cause for concern.
Every house is different, and the location of the hot water heater determines what, if any, sounds are heard. Commonly located in the basement utility room, the garage, or some other out-of-the-way location, the hot water tank’s ‘normal’ noises aren’t bothersome. Some water heaters, however, are located close to kitchens or washrooms where hot water is frequently required, so noise may be more noticeable.
Different brands and water heater qualities produce sound levels that commonly range from 50dB to 75dB. There are some products that claim to be around 40dB, and others have been found to emit ‘normal’ sounds up to 95dB. If you start hearing unusual noises like groans, bangs, screeches, or hissing coming from it though, it’s time to get up and check it out.
Is a Noisy Water Heater Dangerous?
Most modern, properly installed and well-maintained water heaters are not dangerous. If you play with the electrical or gas hook-ups, that’s a different story. Additionally, hot water without a working T & P Valve (temperature and pressure relief valve) can create an explosive situation too, which is a concern with older installations. A noisy poorly maintained and installed water heater is a problem in the making.
Most hot water tanks will last between 7 and 15 years before they begin to fail due to lack of maintenance or service. However, they may begin to use more electricity or gas before that to heat the water if the heating element is covered in sediment. Different, unusual, or irregular noises from the hot water tank indicate different problems. The sound often hints at the type of problem, which, in turn, helps identify the solution.
Some noises may indicate a leak in the water tank or system. A tank that bursts or leaks can spew hot water which can scald and also cause water damage. Additionally, water and electricity can create other concerns too. So, while a water heater isn’t normally dangerous, noises can indicate that it may be becoming so.
Pro Notes: Rental hot water tanks commonly have a maintenance agreement and warranty which requires professional service technicians to perform – contact the provider for service. If you have a gas or propane hot water system and you smell gas, have all occupants and pets exit the building and contact the gas company.
Common Water Heater Noises: Causes and Fixes
Water heaters often stand in isolated locations and are taken for granted. They make different sounds; some are normal, others are warnings that something isn’t right. There are several common causes for water heater noise.
Check the water pressure on the household cold water feed line, it should be between 40 and 60psi. High pressure can cause different noises to occur, plus damage to appliances and plumbing. If there isn’t a pressure gauge on the line, have a plumber install one for you.
Another major cause is sediment buildup in the bottom of the tank. The sediment can interfere with the heating element and result in a variety of noises being generated. The sediment may be caused by mineral build-up or by waterborne particles dropping out of the flow as the water sits in the tank. Mineral build-up can also coat the heating element, reducing its efficiency, cause noises, and damage the appliance. Check out Water Heater Maintenance Tips below.
1. Vibrating Noise
Does your hot water tank vibrate when you turn on a hot water faucet or when the heating element cycles on?
Check that the vibration is coming from the tank, you may be able to feel the tank vibrating as well as hear it. The vibration may be caused by sediment build-up, causing heated water to percolate through the sediment as it heats, generating the vibration.
A related cause is that the heating element may have become loose with time, causing it to vibrate as water flows around it. Coldwater flowing into the tank can also cause vibrations as the hot and cold-water mix. Another cause is the water pressure being set too high.
How to Fix
Check the water pressure in the house and ensure it is between 40 and 60psi. Adjust if necessary.
To remove sediment, follow the directions in the Water Heater Maintenance Tips section below to prevent flooding the area around the tank. Either drain the tank fully or until the outflow is clear.
With the power and water off to the tank, and the tank empty from clearing the sediment, you may wish to tighten the heating element if possible or remove it to inspect for mineral build-up. Make sure you have a new one on hand for a replacement just in case.
2. Rumbling Sound
A rumbling sound coming from the hot water heater when it is heating water can be disturbing and is a sign not all is well with the tank. You may notice the water is hotter too, which you may feel is a positive, but it could lead to a ruptured tank and a flood.
The most common cause of water heater rumble is due to sediment build-up. Sediment may be from minerals or particles suspended in the water which drop out as the water sits in the tank. When the heating element heats the water in the sediment it causes it to expand. As the water expands and escapes through the debris it displaces some sediment and is replaced with cooler water, generating the rumbling noise.
How to Fix
Removing loose sediment is relatively easy, however, the longer the sediment has been present, the more difficult it may be. Follow the directions under Water Heater Maintenance Tips and drain until the water is clear or the tank is empty. If the rumbling continues after maintenance, consider replacing the unit as the sediment has likely hardened and will cause the water heater to fail.
3. Crackling, Sizzling, Hissing
Crackling, hissing, and sizzling noises emanating from the water heater frequently occur when the heating components have become covered with mineral deposits or scale, or sediment.
Hard and soft water contains minerals, which, over time, can coat the inside of the tank, including the heating elements. The heat from the element causes the crackle, sizzle, and hiss as it heats the water. Crackling can be caused by condensation on the gas burner, which is normal but annoying.
Sizzling may be caused by a leak, so check for water around the tank. Another reason the tank is hissing or sizzling could be due to a blocked or failing T&P valve. Gas water heaters often produce condensation which sizzles as it falls onto hot surfaces, it usually stops when the tank water temperature reaches 115°F.
How to Fix
Drain the tank as you would to remove sediment. Once the tank is empty, remove the heating element(s) and place it in a sink, tub, or bucket filled with vinegar. Let soak for an hour or so, and then scrub clean.
You may need a wire brush to get the mineral off. Once clean, insert and re-connect. If the noise is coming from the T&P valve, turn off the power and contact a plumber.
4. Popping / Bubbling Noise
Popping or bubbling noises from the hot water tank usually begin slowly and after several years of quiet operation. It takes time, sometimes years, to build up sediment on the bottom of the tank and mineral scale on the inside walls of the tank. Sediment may be microscopic particles of silicate, grains of sand, or even small stones and other waterborne particles.
Noise caused by water trapped beneath or inside mineral and sediment deposits will pop or bubble as the heating element heats up. Pockets of air or water trapped in the debris expand and generate a popping or bubbling noise.
If the sediment deposits become severe, they can cause the heater to overheat, leading to cracks and leaks. An aluminum anode rod is another common culprit for popping noises, so if the noise isn’t caused by sediment, it’s probably the rod.
How to Fix
To remove the sediment, drain the tank. The sediment will hopefully be drawn out as the water flows out, leaving the heating elements clear of mineral and sediment build-up. For full instructions, check out Water Heater Maintenance Tips below. With the tank drained, check the anode rod for scaling, clean it, or replace it with a magnesium or zinc anode rod.
A humming sound emanating from a water heater may occur at any time, even with new installations. Although the sound can be bothersome, it usually isn’t going to damage the heater.
Water heaters have one or two heating elements. One is always at the bottom and, if there is a second one, it is at the top of the unit. Regular operation of the water heater can cause the heating element to become loose over time, or it may not have been fully tightened at installation. The movement of water through the tank causes a normal vibration or humming sound.
How to Fix
Locate the heating element(s) and tighten the connection. You don’t have to drain or turn anything off for this repair.
6. Knocking, Banging, or Hammering
Knocking, banging, or hammering sounds when the tank is heating water differ from the loud bang you may hear if you shut the hot water off quickly at a faucet, or possibly even when a toilet is flushed. The type of noise, however, indicates the cause.
Knocking, hammering, or banging noises when the tank is heating water are often caused by sediment or mineral build-up. The build-up decreases the space at the bottom of the tank and can often trap water and create air pockets. The noise comes as heated water or steam works its way through the scale or sediment.
A loud banging or hammering when a faucet is closed quickly or a toilet flushed indicates a water hammer. A water hammer can cause pipes or joints to burst, or damage appliances, including the water heater. The water hammer may be due to pressure or the expansion and contraction of the pipes as they are heating. Turning the water off suddenly or even flushing the toilet can abruptly stop water flow into or out of the water heater, causing a pipe to bang or knock in the line.
How to Fix
To stop the banging, knocking, or hammering, remove the sediment by draining some or all of the tank. Follow the directions in Water Heater Maintenance Tips.
A water hammer arrestor installed on the line between the water heater and whatever fixture or appliance is causing the bang will solve the water hammer noise. If the hammer occurs with more than one faucet or toilet, a whole house water hammer arrestor is recommended.
7. Singing, Screeching, or Screaming
Whether nerve-racking loud or quietly irritating, a singing, screeching, or screaming hot water heater demands attention. It may be something simple and harmless, or it could indicate a potentially explosive situation.
A singing, screaming, or screeching sound that occurs when water is flowing in or out of the tank often indicates the water flow into or out of the water heater is restricted. However, if the noise continues when no water is moving in or out, but the tank is heating, then the noise is likely the result of a blocked or failing T&P valve. The T&P valve releases excess pressure within the tank, so if it is screaming, there’s a big problem.
How to Fix
An easy fix for screaming, screeching, or singing when water is flowing in or out of the tank, is to check that the intake and outlet valves are fully open. A restricted valve will be noisy.
If the sound is emanating from the T&P valve, it usually means the water temperature has risen above 210°F in the tank or it has exceeded the valve’s pressure limit (commonly 150psi) and may be approaching the tank’s limit (160psi). The valve should release some water to lower pressure in the tank, which will make the noise. However, the valve is usually silent, so by making noise, it’s telling you something is wrong.
The issue may be the valve is failing, the pressure within the home’s water system needs regulating, or the water heater thermostat is failing. It is recommended that a plumber be hired to service the issue, especially if it becomes a common occurrence.
8. Thump Noise
A thumping sound emanating from your water heater when it is heating water is disturbing, especially in the middle of the night when the house is quiet.
The thumping can occur when sediment builds up around the heating element or on the bottom of the tank. The sediment hampers heat transfer and generates steam bubbles. The bubbles rise upward into colder water and collapse, implode, or condense, with a muted thump instead of a bang.
How to Fix
Draining water from the tank (see Water Heater Maintenance Tips below) may remove sediment and alleviate the noise. If this doesn’t work, consider getting a water softener to eliminate sediment build-up. Thumping, although annoying, won’t damage the water heater.
9. Ticking or Tapping
Ticking or tapping may be from water delivery pipes expanding and contracting as they heat up and then cool down. If it’s coming from the hot water heater though, it’s most likely from a check valve or heat trap in the pipes connected at the top of the tank. Although irritating, ticking and tapping aren’t uncommon or dangerous.
Some water heaters have inlet and outlet connections with heat traps or nipples which can cause ticking or tapping. Heat traps or nipples store heat, improve the water heater’s efficiency, and prevent water from flowing backward in the pipes.
How to Fix
If the noise really bothers you, replace the connections with trap-less fittings or dielectric nipples, but make sure the sound is coming from the tank and not the pipes.
10. Water Heater Making Noise Like Water Running
The sound of water running when all taps are closed and no toilets are filling is very disconcerting. It’s normal to hear water running as cold water flows into the tank to replace hot water being drawn to sinks and tubs. However, if no water is in use and the sound of running water seems to be coming from the water tank, there’s a problem.
The sound of running water when all faucets are shut usually indicates a leak. Moisture or water on the floor or seeping out under walls is a sure indication you have a leak. If there is no sign of a leak, check the T&P valve, especially if it connects directly into a drain. A faulty valve can release a continuous flow, resulting in the sound.
How to Fix
If the water is leaking from the water heater, turn off the cold-water supply and shut off the electrical breaker or turn the gas to “Pilot”. Affix a hose to the drain spigot near the bottom of the tank and drain the tank into a floor drain, sump pump hole, or outside. Be careful as the water will be hot. Contact a plumber to replace the tank, or replace it yourself.
If the water is running out of the T&P valve, then toggle the lever open and closed. If the water flow doesn’t stop, shut the water feed off, turn off the power or turn the gas to “Pilot” and replace the faulty T&P valve.
11. Water Heater Still Knocking After Flush
If the water heater is still knocking after the tank has been drained and flushed of sediment, you can try again or contact a plumber for assistance.
The knocking may be caused by hardened sediment that didn’t, and may never, drain out. It may be due to mineral scaling on the heating element or hardened chunks of sediment or pebbles that are too large to drain out.
How to Fix
There are several solutions for addressing the knocking sound after the tank has been flushed. If the sound is caused by hardened sediment, replacing the tank and following a regular maintenance regime with the new tank is best. Alternatively, removing and cleaning the heating elements, or replacing them may solve the knocking noise. Adding a water softener ahead of the water heater may address hard water sediment build-up and, over time, diminish existing sediment.
Tankless Water Heater Noises
Tankless water heaters, whether electric or gas, commonly produce less noise than a tank water heater. However, they do make ‘normal’ sounds, as well as unusual ones too.
- A clicking sound occurs when the water flow starts or stops, and is ‘normal’.
- Calcium deposits or scaling can cause louder noises, so if you have hard water, a water softener may help.
- A knocking or scraping is frequently due to dirty fan blades or debris lodged on or in the fan on gas units.
- Squeaks and squeals usually are the result of a faulty fan bearing on combustion heaters.
- A hiss or whistle can result from a sealed combustion chamber leak, which will also result in irregular combustion and poor efficiency.
Water Heater Maintenance Tips
Regular maintenance is the best way to prevent water heater noise and extend the life of the heater. Service and care don’t usually take very long, and ensure you catch problems before they spring a leak.
To Prevent Sediment Build-up
- Every two to three months place a bucket or pan under the tank’s drain spigot, open the tap, and run the water until it is clear, usually, a gallon is all that is required.
- Installing a water softener on the cold-water feed line, where it enters the house, will help remove hard water sediment before it reaches the hot water tank. Less sediment means less chance of noise, and longer life for the water heater.
To Remove Sediment
- Turn off the cold-water feed valve.
- Turn the water heater power off at the breaker or turn the gas temperature setting to “Pilot” and let it cool for about 2 hours – to prevent scalding.
- Attach a garden hose to the drain at the bottom of the tank and place the other end at the floor drain, in a bucket, or outside the house.
- Open a hot water tap on a faucet to prevent a water vacuum from forming.
- Open the drain valve and let the water pour out – you may empty the tank or run the water until it is clear.
- Open the supply line for 5 or so minutes once the tank is drained to flush more sediment out – repeat until the water coming out the drain is clear of sediment.
- If little or no water drains out, remove the hose and use a screwdriver or metal rod inserted into the drain 2 to 3-inches to attempt to loosen the debris. Have a pan or bucket available to catch the water once the blockage is removed. Reattach the hose and continue to drain the tank.
- When the water is clear or the tank drained, close the valve, open the water intake valve, and fill the tank. Turn off the faucet once the air is out of the line and open it once the tank is filled to let any trapped air out. Power up the hot water tank.
- Flushing the tank annually with a deliming solution, or having a local plumber do the flushing, will prolong the life of the tank and minimize noise concerns.
- Tighten the heating element(s) once a year, or if the tank is vibrating when heating.
- Remove the element(s) and soak in vinegar or another approved descaling solution if the tank makes a humming, crackling, sizzling, or hissing noise.
Inspect the T&P Valve
- Regularly check the T&P valve works. Toggle up or lift the valve lever to open the valve and listen or observe water draining from the valve for 5 to 10 seconds. The water should stop and not drip when closed. If no water comes out, or it won’t close properly, it may be partially or fully plugged and should be replaced.
Check the Anode Rod
- The anode rod, like the heating element(s), is inside the tank, so it is difficult to check without removing it.
- The anode rod protects the lining of the tank from mineral deterioration, which makes it an important component to check.
- A popping or bubbling sound commonly indicates scaling on the anode rod.
- A rotten egg smell new to the hot water means the anode rod has deteriorated and should be replaced.
- Replacing an aluminum anode rod with a zinc or magnesium rod may solve the noise and smelly hot water issues.
Check the Temperature Setting
- The water temperature is often set at 125°F. It can be reduced to 110°F which will extend the life of the tank and reduce noise-causing pressure. Hot water tanks set at the upper limit of 140°F may bleed out more frequently at the T&P valve and create more pressure which can result in a shorter tank lifespan.
- Another possibility is to install a thermal expansion tank. It will prevent water backflow, T&P valve seepage, and water pressure fluctuations, all of which may cause disruptive noise over time.
Water Heater Alarm
- If you are concerned that your water heater could leak, install a water heater alarm. Different models have alarms that scream between 90dB and 110dB to warn that the tank is leaking. Some models even link to apps on phones, tablets, and computers to warn you if you’re not at home.
Noises coming from a water heater often indicate what the problem may be, so knowing what the sounds mean is important. Regular maintenance and service will keep your hot water heater working quietly and efficiently for years. Hopefully, you have a better understanding of what different sounds mean, and how to maintain your hot water heater for years of use.