The Ultimate Guide to Whistling Water Heaters and How to Fix Them

Last Updated On June 11, 2024

Updated on April 14, 2023



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water heater whistling what does this mean

Help! My hot water heater is whistling and making high-pitched noises! Why does my water heater emit a whistling or hissing sound, and how can I resolve the problem? 

Whistling noises can occur in tank-type water heaters due to sediment buildup, but it can also happen to tankless water heaters if the TPR (temperature – pressure relief valve ) becomes damaged and can’t release pressure at the required rate. 

Not sure what to do about your whistling water heater? Continue reading for more details.

In this PlumbingNav guide, we will cover:

  • Causes of Water Heater Whistling Noises
  • Possible Danger to Consider with a Faulty Water Heater
  • How to Stop a Water Heater From Whistling or Squealing

Safety Warning:

Whistling noises from your water heater indicate a serious problem with the unit and require immediate attention. DO NOT IGNORE OR PUT OFF A WHISTLING SOUND COMING FROM YOUR WATER HEATER!

What's In This Guide?

      Why Is My Water Heater Whistling?

      Water heaters can whistle for a variety of reasons, but the two main causes are a damaged water heater tank and pressure buildup. We will cover these two causes for water heater whistling in detail and what that could mean for your water heater, your home, and your safety. 

      1. Cracked Water Heater Tank

      Cracks can develop in your water heater tank due to corrosion. When the corrosion process starts, it will eat at the metal of the tank until it breaks down. If the tank does get a crack, the air escaping from it can create the whistling sound you hear. 

      A cracked water heater tank can lead to frustrating leaks and possibly even water damage, but you don’t need to worry about an explosion with this issue. 

      2. Damage Due to Corrosion

      You can spot corrosion in your water heater tank by visually inspecting for rust around the valves and connections of the water heater. You may also notice discolored water or water with a funny smell similar to rotten eggs

      The most dangerous aspect of a corroding water heater tank involves the metal content that contaminates the water. 

      Safety Warning!  

      Do NOT drink water from a corroding water heater. Water with copper levels of 1.3mg/L or higher and lead levels of .015 mg/L or higher can lead to health problems. 

      To prevent rust and tank deterioration, take the following actions:

      • Replace your sacrificial metal anode rod every 3 – 5  years as necessary. Or if the corrosion has removed more than half of the anodes original size.
      • Apply anticorrosive coating to the inside of the tank
      • Buy a water softener

      3. Pressure Buildup

      Excessive amounts of pressure in your water heater can literally lead to an explosion. While rare due to the safety measures manufacturers include in each unit, you want to act quickly when you notice high pressure levels. 

      As pressure builds up, it puts stress on the tank. The tank may start to whistle, shake, or even spring a leak. 

      Once again, the pressure buildup could derive from sediment deposits. Even if it doesn’t cause the unit to explode, you will surely run into some inconvenience, to say the least. 

      Some reasons for pressure build up in a water heater include:

      • Too high of a temperature setting
      • Thermostat faulty due to sediment buildup
      • High water flow speeds
      did you know water heater whistling noises

      Dangers Of A Faulty TPR Valve

      Pressure buildup in your water heater will whistle if the TPR valve automatically activates to release pressure. This safety heater mechanism generally reduces the likelihood of danger, but a faulty TPR valve can allow the pressure to build up to levels that lead to an explosion. 

      Where Do I Find the TPR Valve? 

      On most water heater models, you will locate the TPR valve at the top of the unit. You will find it attached to the drain line ( or “discharge pipe”). This isa pipe almost the entire height of the water heater that sits on the outside of the device. 

      You will identify a faulty TPR valve when the unit leaks at that connection or if you notice pressure problems in your water heater. Luckily, you can usually activate the pressure relief valve manually and replace it to prevent the problem from happening in the future. 

      How Do I Know If My Water Heater is in Danger of Exploding?

      How do you know the difference between a faulty yet innocuous water heater and a potential water heater bomb? Check for the following indicators that you have a serious problem on your hands. 

      1. Perpetually Open TPR Valve

      If your TPR valve doesn’t fully close, it signifies a constant need to relieve pressure in the tank. The stress from the high pressure levels can also lead to leaks around the temperature and pressure valves. 

      2. Signs of HIgh Sediment Deposits

      If the high pressure levels in your water heater derive from problems related to sediment deposits, you may notice:

      • Discolored water
      • Water with a rotten egg smell
      • Increased water temperatures

      How To Stop A Water Heater From Whistling (5 Steps)

      A whistling water heater generally indicates the end of the life of your water heater. When components start going out, such as the TPR valve or heating element, you may want to consider a replacement. 

      With that being said, for relatively new water heaters with a sturdy tank, follow these steps to stop a water heater from whistling. 

      1. Safety First

      As always, start by turning off power to the unit and taking special care to keep yourself safe throughout the process.

      2. Completely Open Pressure Valve (Replace if Necessary)

      Completely open the pressure valve on the unit. You can do this by raising the valve up. Ideally, pressure and water will escape from the drain valve at the bottom of the unit. If you can’t open the valve, you may need to replace it. 

      3. Lower Temperature 

      Use your water heater manual to learn how to turn the temperature down on your specific unit. You will eliminate water heater buildup by keeping the temperature below 120°F

      If the water heater still produces water at excessive temperatures, you probably have sediment buildup on your thermostat or heating element. 

      It’s possible to have sediment buildup in the TPR itself that causes it to malfunction. This might prevent it from releasing excessive pressure and heat. This could also be dangerous so have it checked out by a professional plumber.

      4. Flush Water Heater

      Eliminate calcium buildup by flushing the water heater. After you let the water fully drain out of the tank, fill it up and drain it again. Repeat the process until you no longer see sediment in the water. Generally speaking, you should do this once a year. 

      5. Install Water Softener

      Hard water causes more sediment accumulation. If you notice soap scum on your dishes and sinks or stiff laundry, you should install a water softener. The water softener will reduce future build up. 

      Bonus Video: Mythbusters Explodes Water Heaters!

      Now that you avoided imminent danger, enjoy the video below of MythBusters hosts Adam Savage and Jamie Hynerman blowing up a water heater tank. 
      Do NOT try this at home (on purpose OR by ignoring water heater maintenance or putting off tending to a whistling sound from your water heater).

      Other Noises? How to Troubleshoot A Popping Water Heater 

      What if your water heater is making other noises? A water heater making popping noises or banging noises may have different issues than one making whistling noises. Usually, the tank contains too much sediment buildup in this case

      Sediment accumulation develops naturally after time, especially in areas with hard water. The more minerals in the water, the more likely you will find calcium deposits left behind. When water heats, it expands, and this can lead to sediment buildup, especially if you set the water temperature or water pressure too high. 

      Perform these steps to diagnose and fix a popping water heater for good:

      • Step One: Check and adjust water temperature (120°F or lower)
      • Step Two: Check and adjust water pressure (under 50 psi)
      • Step Three: Look for signs of hard water and buy a water softener if necessary
      • Step Four: Flush water heater
      • Step Five: Swap out aluminum anode rod for magnesium anode rod and set a reminder for yourself to check it in a year

      See this related post about why plumbing pipes make noises if you also notice sounds coming from elsewhere in the home, and not just your water heater.

      Quick Read FAQs

      Is a water heater whistling dangerous?

      Not usually. Water heaters have safety measures in place to prevent a dangerous situation in most cases. However, a whistling water heater usually leads to leaks and potential water damage. On rare occasions, if the safety features don’t work properly, a whistling water heater may explode. 

      How do I stop my water heater from whistling?

      To stop your hot water heater from whistling, start by opening the pressure relief valve all the way. The whistling may get louder for a moment, but it should ultimately stop the whistling once you relieve all of the pressure. 

      If that doesn’t resolve the problem, try the following troubleshooting steps:

      • Lower temperature
      • Flush water heater tank to remove sediment from thermostat/heating element
      • Lower pressure levels

      Why is my hot water heater whistling?

      Water heater whistling generally derives from water heater pressure buildup in the tank. The pressure accumulation in the tank is often caused by a faulty pressure valve or sediment deposits.

      How do you know if your water heater is going to explode?

      You know your water heater may explode if the TPR valve never closes. You may also notice leaks at the temperature and pressure valve.

      Alternatively, you may notice an unappealing color and smell to your water as well as excessively high water temperatures. These symptoms indicate the problem comes from sediment buildup as opposed to a pressure valve problem. 

      However, when you don’t know for sure, assume the worst and stay safe. You may even need to break down and hire a professional plumber.

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      About Plumbing Navigator

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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