Why My Water Heater Makes Noise

411 plumb Your water heater can make noise in a variety of ways ranging from hissing, popping, tapping, banging, and even jackhammer sounds. Some are indicators of problems while others are just age and improper maintenance that really are not much of a concern but will go away when the water heater is eventually replaced.

A hissing or, popping sound when the water heater is reheating is one of the more common sounds a water heater makes. When water is heated the water molecules expand taking up more room leaving less room for other things in the solution. The hardness minerals dissolved in the water such as lime feel this molecular expansion and precipitate out of the solution falling to the bottom of the water heater. The minerals build up on the bottom of the water heater and if you do not periodically flush the water heater will eventually coat the bottom of the water heater and may even cover the lower element in an electric water heater. This thick layer of minerals acts as insulation and keeps the water from having direct contact with the element of bottom of the tank. Water entrapped in the blanket of minerals being heated by the element on an electric water heater or, by the bottom of the tank on a gas water heater actually makes a series of small steam explosions as it is heated making hissing and popping sounds. If you have waited this long to flush your water heater the build up is probably quite hard and will not break up with just flushing. With gas water heaters the efficiency of the units will suffer, as the heat does not pass through the blanket of minerals as efficiently. With electric water heaters the build up covering the lower element will also affect heat transfer and many times will cause the element to overheat and burn out. With electric water heaters it is possible when changing a lower element to reach in through the hole for the lower element and break up the minerals so they may be flushed out.

A tapping noise or, buzzing noise when water is flowing can be caused by heat traps installed on the inlet and outlet of your water heater. Heat traps are basically small automatic valves that seal the inlet and outlet of the water heater when water is not flowing keeping the heat inside the insulated water heater instead of allowing the heat to escape into the pipes where it would be lost. Some manufacturers use heat traps that use a mechanism like a marble to seal the heat in. When water is flowing the “marble” moves in the flow making a tapping noise. Other manufacturers use heat traps, which have a flexible flapper type valve. This flexible flapper may vibrate at certain flow levels causing a buzzing sound when water is drawn. These sounds are generally harmless and will seem loudest at the inlet and outlet although the sound may transmit some distance away.

A banging noise when the water is shut off is usually water hammer. Water hammer is caused by the momentum of the water moving in the pipe coming to a sudden stop. The noise will often be a series of bangs louder at first and tapering off then stopping. Pipes that are not properly secured moving from the momentum can be a cause as well as excessive velocities of the flowing water in the pipes. Undersized pipes, and or, excessive pressure can cause the higher velocities. The pressure of your water supply should not exceed 80-psi and if it does a pressure-reducing valve should be installed in most cases with the pressure-reducing valve a thermal expansion tank should also be installed. Excessive velocities in a pipe may cause erosion of the pipe material resulting in leaks. Water hammer is a problem that may cause damage to components of your water supply system and should be addressed.

Jackhammer sounds are almost always accompanied by pulsations in the flow of water. This is usually caused by something loose in the stream of water, which in a sense is turning the water on and off rapidly making a constant series of water hammer type noises. These noises will often vary with the flow volume and may often disappear or, appear only within a certain flow range. Many times the loose debris may be a rubber washer on a valve that has come loose often from recent use. This is something that should be addressed as often it indicates a valve that will no longer function.

In any case while some noises may be harmless and not require any attention some may be serious and require repairs. For your safety it may be best to have a plumber check the noise out for you and determine its cause and if repairs are needed. Some noises particularly those relating to a gas burner operating on a water heater may be very serious and it is better to be safe than sorry.

Posted in plumbing questions, Water Heater Repairs Tagged with: ,
77 comments on “Why My Water Heater Makes Noise
  1. Lauren says:

    Hi, I looked through the forum and didn’t see a match for our problem, but sorry if it’s a repeat.

    We have a 50 gallon 40,000 BTU gas water heater (Bradford White model# MI5036LN10). It was installed in 1998. I know it’s probably at the end of it’s life anyway, but I’m hoping you can give some insight to what’s going on.

    After it runs a heating cycle (after using hot water) and the burner turns off, I hear 3-5 metallic clangs. Then it’s quiet until the end of the next cycle. Nothing during the heating, only after.

    I will admit, we haven’t flushed it regularly. We flushed it about 4 years ago when we moved in (and I doubt the previous owners did anything). Could it just be that we killed it by letting sediment accumulate and harden?

    Thanks in advance,

    • Redwood says:

      Hi Lauren,
      This is just a guess as I’m not there to inspect the water heater, but I would guess the flue baffle has probably deteriorated, and you will probably be seeing soon if not already, a decrease in efficiency, and a possibly dangerous rise in flue temperature. I’d plan on having a plumber inspect the water heater and possibly replace it ASAP.

      Hope this helps,

      • Lauren says:

        Hi Redwood,

        Thanks for the speedy reply. You wouldn’t happen to be in the Chicago area? I could really use someone like you.

        Do you have an opinion on tankless water heaters? Are they worth the extra money?

        We are in a condo and are looking to sell this place as soon as the market recovers some (hopefully in the next few years). While the tankless would look good for resale, it probably wouldn’t help the bottom line. And only being here for a few more years, we won’t see the return in energy savings.

        So the question is, to tank or not to tank…

        Any input would be greatly appreciated!

        Thanks again,

        • Redwood says:

          Hi Lauren,
          Unfortunately it would take me a couple of days to drive there, but on one of my other websites I have a list of plumbers (click here) and in the Chicago List the only plumber on there is a good friend of mine. Give him a call you’ll be in good hands. Tell Richie that Redwood sent you!

          As for tankless water heaters, I’m not a big unless you want an unlimited amount of hot water at a regulated flow amount. The conversion may require a larger gas supply line, and will require intake air and a different exhaust vents to be run. I’m not sure of the costs in the Chicago area as costs vary greatly in different market areas around the country but here the installation of tankless could easily be 3 times the cost of a tank style water heater replacement. I would suggest reading “Tankless Water Heating Guide” (click here) for additional information.

          There are some ultra high efficiency tank water heaters available that would eliminate the unpleasant hot cold water sandwich that comes with a tankless installation without a recirculation loop, but they tend to be quite expensive as well.

          Hope this helps,

  2. wanda says:

    Hi, I noticed a couple days ago as I passed in front of the water heater that it sounds like a air conditioner sound, and it hasn’t stopped. Is it something I should worry about?

  3. Mary says:

    Hello. It’s kind of you to post replies. I turned the water off at the house and put the water heater pilot at ‘vacation’. When I sometimes spend the night at the house an occasional popping sound occurs, and it sounds like it’s coming from my heat duct near the floor. It sounds like a plastic bottle being squeezed or like a vent lid bouncing from the wind. I know it sounds weird. I can’t be home again for a few days but I will call a plumber asap, probably from your list. In the meantime any idea?

    • Redwood says:

      Hi Mary,
      It’s hard to say based on your description. Heck, is there a loose vent cover? Can you identify more possible conditions such as when the sound happens? Does it happen completely random or, while the burner is on? It may be expansion of the flue pipes or, possibly thermal expansion if it happens while the burner is on.

  4. Rose says:

    Hello and HELP!! It was 4:30 am and I got up to let my cat out then heard a hissing coming from the garage, thought something was happening to my car. It’s coming from the water heater. I turn the unit off at the breaker box when I don’t need hot water for a day or so if I.m away. I rent and have been here for 8 years. No, I never knew I should drain it and the landlord never mentioned this either. Besides the hissing, there is water on the garage floor in a stream from the bottom of the heater. What’s your take on this?

    Thanks for being awake at this hour I’m in Oregon) now it is 5:24 am. -Rose

    • Redwood says:

      Hi Rose,
      You need to take a look at the water heater and see where the water is coming from. If the water is coming out of the T&P valve (The valve with the lever on it, that comes out of the side or, top of the water heater), the drain valve or any of the associated pipes then a repair can be made. If the water is coming from the water heater tank itself then the water heater needs to be replaced. In addition to the circuit breaker you need to shut off the valve on the inlet side of the water heater to stop the flow of water out of the leaking tank.

      Call your landlord right away to let them know you have a leaking water heater, and to have them send a plumber to fix it.


  5. Michelle says:

    Okay so our water heater is making a sound like there’s water running, but I didn’t find any leaks or see and puddles. It got pretty cold a few days ago so some of our pipes froze, and only cold water would come out of the faucets, but no hot water at all. What could be wrong with it? We shut off the main water valve and the noise stopped, but I don’t know if I should turn it back on since I am not sure whats wrong.

    • Redwood says:

      Hi Michelle,
      I suspect that a pipe has frozen and burst or, just developed a leak. I also suspect that your home is on a slab so the the leak is occurring in a location where it cannot be seen. If you are able to look at your water meter with the main valve turned on, and everything else shut off, I’m sure you will see the meter spinning.

      I’d recommend leaving the water off and calling a plumber to locate and repair the leak. If you want a good plumber, I have a close personal friend of mine who is in Gilmer, you can call him at (903) 841-0062, and tell him Redwood sent you.

      Hope this helps,

  6. Karen says:

    Just in the last month or so I have notice a noise like pipes clanging not real loud with my water heater . It happens several times a day. I think it is when it’s heating the water. No any other noise. I’ve looked all around it and that seems to be the only problem. It’s maybe about 5 yrs old. Never had any problems. No leaks anywhere. Could you give me a little advice?
    Thanks, Karen

    • Redwood says:

      Hi Karen,
      There could be a wide variety of reasons ranging from minor to deadly serious. It would help to know if this is an electric or, gas water heater and perhaps the brand and model# if you can get it off the tag on the unit.

      On the dangerous side, sometimes in a gas water heater the flue baffle inside the water heater can sometimes come loose and fall down onto the burner. When this happens the exhausting flue gasses go up through the water heater too quickly and not enough of the heat goes into the water so in addition to being very inefficient the flue pipe becomes overheated and may create a danger of fire.

      Another dangerous situation is on either gas or electric water heaters when there is a check valve or a device that acts at a check valve which creates a closed system, in which several devices such as a thermal expansion tank, T&P Valve, Thermostat and a ECO, can cause a situation where dangerous pressures can build in the water heater. In some cases the pressure can go so high the pipes feeding into the top of the water heater will bow inward on gas water heaters, and outward on electric water heaters. This is a dangerous situation where the water heater may explode. Search T&P Valve, Thermal Expansion Tanks here on 411Plumb to read more.

      Some of the minor problems could be water in the pipes making drastic changes in temperature quickly, such as pipes with warm water sitting in them from being inside the house without the water running, then when you turn on the water cold water comes in from outside casing the pipes to contract or, the water in pipes coming out of the water heater have cooled off to room temperature then running hot water brings in hot water causing expansion.

      Another minor problem could be water hammer in which pipes make a hammering sound when a valve is suddenly closed with the momentum of the moving water causing improperly secured pipes to move and make a hammering noise.

      Sometimes power vented gas water heaters make noises when the light, or the fan makes noise, these will usually be a sign that you are soon going to have reliability problems.

      I’d take a look and see if those 2 minor problems are what is going on and just see if you can see what is going on. With more information we can probably get a better idea of what is happening. If you see dangerous symptoms such as the bowing pipes you should shut the water heater off right away and call a plumber to make repairs as well as replace the water heater.

      Hope this helps,

  7. john c says:

    We have a hydro jet mi50t6ds. Today the hot water stopped working, I opened the compartments to see if I could shut the power off and then restart, I pressed the red button and the heater began this hissing sound. I do not smell gas, but the hissing sound worries me. I immediately closed everything up.
    The water remained cold. Is there anything I can do before the plumber comes tomorrow?
    thank you

    • Redwood says:

      Hi John,
      I believe smelling gas won’t be a problem with your electric water heater and maybe by morning you might have hot water, But it certainly sounds like your water heater needs repairs. The water heater had shut itself down because it got too hot and the ECO or, energy cutoff otherwise known as the “Red Button” had tripped. Excessively hot water in the tank is the only reason this trips.

      There are a couple of reasons why this would happen you can read about them here: Electric Water Heater Red Reset Button Tripping Troubleshooting Guide

      When you pressed the red button you again supplied electricity to the water heater and since it was cold the top element started heating (as long as the upper thermostat is operating correctly), however my educated guess is that the top element has shorted out and the metal sheath of the element has a hole in it which allowed water inside the element making it hiss when it started to heat. Because the element is shorted it allowed the water heater to continue to heat with the unswitched leg of the 240 volts which continued to heat the water in the tank with 120 volts to ground, causing it to overheat and trip the ECO as outlined in the article I linked above.

      Your plumber may be able to rebuild the water heater for you rather than replace it if the water heater is in good condition. He may however based on his observation and knowledge of the life expectancy of water heaters in your area decide against this and tell you it should be replaced. I’m not going to second guess his opinion from here without his local knowledge. Here I’d expect about 12 years or more out of a water heater, your area could have considerably less of a service life, I don’t know.

      If he does elect to repair the water heater I would probably expect that both thermostats (Upper and Lower) would be replaced along with both elements. I usually troubleshoot the water heater to find the exact component that has failed, but elect to replace all of those parts. My opinion is that I’m there and the cost of all the parts is not that expensive, so it is better that I replace them all to ensure the water heater operates correctly for a long time. It costs more to go back a second time to replace another failed part both in time, and the customers opinion of the quality of my work when I fix something and it dies again a few weeks later. Trouble shooting to the failed component assures that the new parts I install fix the problem and there is not another problem.

      One other thing I like is, to replace the elements with ultra-low watt density elements like I have written about in this post: How To Replace Electric Water Heater Elements These elements typically have an sheath which is made out of a much more corrosion resistant metal such as Incoloy and the heating is distributed over a much larger area giving the element a much longer service life expectancy, and it is claimed these elements will not burn out even when dry fired, although I wouldn’t recommend doing so. These elements are so much longer that they run cooler, yet still provide the same amount of heating a smaller sized element does, it’s just the heat is distributed over a much larger area.

      Please feel free to share these linked articles on 411Plumb with your plumber. He may thank you for doing so, I have shared these with many plumbing professionals and I do often get feedback that they learned something from them. In any case tomorrow your plumber will have an educated consumer, which in my experience is often much easier to deal with. Good luck with your plumber tomorrow and I’m sure you’ll be in hot water soon in his capable hands.

      I hope this helps,

  8. john c says:

    Wow thank you! This may have been the best reply to a post I have ever had! My hot water did return by 5am this morning. I will call the plumber today. Thank you again for the valuable information

  9. lisaburrow says:

    My husband just Installed a gas water heater on 11/4/2013. Whirlpool model#N40T61-343.Here lately I’ve been hearing a pinging sound, almost like a popping sound. Is this something I should worry about? Thank’s Lisa in Dallas Tx.

    • Redwood says:

      Hi Lisa.
      Unless you have extremely hard water it is far to early for a sediment buildup in the tank to be causing the popping noises. I’d suspect a couple of possibilities for a cause.

      • Did your husband install a smaller sized water heater than what was originally there, are you “Running Out Of Hot Water?” An undersized tank will draw down and become cold, the tank will become cold and water will condense on the tank then drop onto the burner making a noise.
      • A hot water pipe leaking under a slab may also cause the hot water to draw down causing condensation. With everything in the house turned off check your water meter to see if water is flowing. If the meter indicates flowing water turn off the valve at the water heater and see if the flow stops.
      • In some homes a “Closed System” may exist on the water supply system which can cause thermal expansion of the water while it is heating to increase the pressure and cause the tank to make noises as it flexes under the increased pressure. Your T&P valve may discharge a small amount of water under this circumstance. I’ve placed several links to articles here on 411Plumb about thermal expansion below this list.
      • The water pipes or flue pipe may have been installed in a manner where the expansion and contraction from temperature changes when the water heater is on or, off, may be causing the noise.

      There could be other causes as well those are just a few possibilities to investigate off the top of my head. If you can’t figure out the cause you may need to call a plumber to diagnose the problem.

      The T&P Valve on my Water Heater is Leaking
      Thermal Expansion Tanks for Water Heaters

      Hope this helps,

  10. T Quinta says:

    We rent a condo and the landlord will not give us a key to water heater cabinet outside the front door.
    It bangs when it reheats the water. It bangs loudly. Is this dangerous or just a noise nuisance? We are fine with the noise. Thanks in advance for your reply.

    • Redwood says:

      Hi T Quinta,
      It is hard to say for sure without being there to see the type of water heater, and examine the operation of the water heater. Noises can be minor with little more than a loss of efficiency, to major with dangerous operating conditions. I would insist that the landlord has a plumber inspect the water heater to determine the cause of the noise. I have described some common noises in the post above and the causes, noises should always be checked to see what they are and a determination made whether or not something needs to be done.


  11. Holly says:

    I just replaced the valve on my water heater Thursday. In the middle of the night last night I heard a loud hissing coming from it. I went up to the attic and shut the water off and cut the breaker off. What could this be was an extremely loud howling hissing noise and the top of the valve was vibrating like it was about to blow? Thank you in advance,

  12. Rod Warrix says:

    Am wondering what happen to my gas hot water tank. Here’s the situation. I have a dog, and she had laid next to the heater for a few days while I was working on things in the basement. I had a box of old news papers sitting in range and did not notice she tipped it over and had pushed tons of them under the water tank. The water went cold and I checked to see why and realized the news papers”!!!” under it and blocking the all holes. One still had plastic bag on it and had burnt to bottom of the base of the tank. About seven new papers in all if not more so completely stuck under no air flow or ability of heat from burner being able to cool. I tried relighting it and it won’t stay lite. The pilot will stay lite as long as the burner does not lite. If burner lights it varys on how long it stays lite about 45 seconds if not been lite for awhile then if relighting 10 – 15 seconds after that. Now their is also a metal ping sound when cooling down from being lite for the 45 secs. Can you help me with what might be the problem and what is wrong. Sounds not too funny but did I burn my water tank up? Water was clean running always from the faucets and I drained the tank to clean it out.

    • Redwood says:

      Hi Rod,
      I suspect that you may just have a blocked air inlet which may be cleaned, however, it also may be a blocked flue and a dangerous condition for both fire and carbon monoxide. I highly recommend hiring a licensed plumber to check the water heater ASAP.

  13. lee says:

    I have a two yr old gas water heater and last night the water hot very cold in the middle of my shower and when I went to check the water heater, I heard a very loud buzzing noise coming from the inside of the water heater. There is a large amount of rust dust on the floor and the hot water has not been lasting as long as it should be. Also, the element needs to be changed and is making the water smell of gas or a smokey smell. Is the water heater in need of flushing and maintenance or is it about to fail?

    • Redwood says:

      Hi Lee,
      It is hard to say exactly what is going on by your description, but the smell of gas or smoke says you should shut off the gas and immediately call a licensed professional to check the operation of the water heater.

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