How Do I Put Hydrogen Peroxide in My Hot Water Heater?

Last Updated On October 19, 2021
how do I put hydrogen peroxide in my hot water heater

Are you noticing a foul smell, like a rotten egg, coming from your faucets when you run the hot water? If so, there is a common and low-cost DIY solution that may help…hydrogen peroxide.

How Do I Put Hydrogen Peroxide in My Hot Water Heater?

In this Plumbing Nav article, we will discuss this in detail. We’ll also cover:

  • What is the rotten egg smell coming from your water?
  • Is hydrogen sulfide dangerous or a health concern?
  • How to use hydrogen peroxide to kill sulfur bacteria?
  • Other options if the problem persists.

What's In This Guide?

      What’s That Rotten Egg Smell Coming Through the Hot Water Faucet?

      It’s not uncommon for rotten egg or sulfur smell to develop in your water heater or your corroded iron piping if you live in an older home. There are a few potential causes of this.

      Even if you receive chlorinated drinking water in your home, this smell may be present. In fact, chlorine in city water might actually be one of the main contributors. The rotten-egg odor tends to occur due to a wide range of factors, mentioned below.

      Factors Causing Hot Water Odor:

      • Low chlorine residual
      • Water that has been unused for weeks
      • High levels of sulfates in the water

      What is Hydrogen Sulfide and is it Harmful in Your Water?

      This last one is often the main culprit behind smelly hot water. Hydrogen sulfide is an anaerobic bacteria that is a colorless chalcogen hydride gas with a characteristic and foul rotten egg odor. These tend to be even more present in hard water. While the gas can be toxic at high levels, its presence in water is not a health concern. It’s just unpleasant!

      Now, let’s identify the true location of the problem behind the smell, and define some terms to aid our discussion about your water system.

      Is the Bad Smell Coming from Your Hot Water Heater?

      This bad smell tends to occur when a reaction between sulfates and microorganisms takes place in the water supply, often in closed containment. This reaction tends to cause hot water tank smells, as they are closed off to oxygen. To confirm if this is your issue, you will have to check if the cold water smells too, or just the hot water.

      -Turn on a cold water faucet and run it for a few seconds. If you still pick up the bad odor, then the source of that rotten-egg smell is in the cold water. However, if you aren’t picking it up, turn off that faucet and move over to another.

      -Turn on the hot water and run it for a few seconds. If you pick up the bad odor here and not when you run the cold water, the source is likely in the hot water heater.

      Is the Smell in Your Hot Water?

      You have two options once you get to this point. You can install a hot water sulfur eliminator kit for ongoing protection to kill that foul sulfur smell. This is a great solution but is more expensive than other DIY options.

      You can also choose to put hydrogen peroxide in your hot water heater, which is more cost-effective and also works very well. Let’s focus on this one.

      We will now explore this DIY option to explain how to do it safely without causing accidental damage to your hot water heater.

      did-you-know-can-you-add-hydrogen-peroxide-to-water-heater

      Simple Steps For How To Put Hydrogen Peroxide In Your Hot Water Heater

      Putting hydrogen peroxide in your hot water heater isn’t as complicated a project, but you will need to follow some specific procedures to do it right. Here are some tips that will help you get it done properly.

      Step 1: Turn Off the Water Heater

      It doesn’t matter which kind of water heater you have (electric or gas); you need to first turn it off before you can do anything with hydrogen peroxide.

      If you are dealing with an electric water heater simply turn it off from the manual switch. You can also kill the breaker. If you have a gas water heater, then you will need to turn the control to the pilot-only setting.

      Note: If you have a gas water heater, ensure that the pilot is still lit. This will allow you to turn the heater back on and restart it once you are done adding hydrogen peroxide to your tank.

      Step 2: Don’t Let Any Water In

      You will need to close the cold water valve to keep any more water from coming into the water heater tank at this point of the process.

      Step 3: Relieve Tank Pressure

      To relieve the pressure you need to open a hot water faucet (preferably one nearby) as well as the T&P valve. This stands for the temperature and pressure valve that is typically located at the very top of your water heater. Opening these two components at the same time will relieve the hot water heater of any built-up pressure.

      Note: If you notice that your T&P valve is somewhat old or defective, it would be wise to replace it to avoid any water pressure issues in the future.

      Step 4: Drain Some Water

      To make room for the hydrogen peroxide that you will be adding a bit later, it’s advisable to drain some of the tank’s water. This is simple enough. All you have to do is connect a garden hose to the drain valve, assuming there isn’t an open drain adjacent to your water heater. Remove enough water to accommodate the opening you’ll use discussed in the next step.

      Pro Tip: It’s advisable to have a hose bib cap handy; these are readily available at your nearest hardware store or online. In some cases, when you are done with the procedure, the drain valve might leak. This is one reason to use a drain pan even if not required by code.

      The hose bib cap is an excellent solution to this problem as you can screw it on at the end of the valve, which will save you the headache and expense of having to replace the drain valve or call a plumber.

      Step 5: Disconnect Outlet Pipe

      Now you need a way to add hydrogen peroxide to the tank, and you have options. You can remove the T&P valve, the anode rod, or simply disconnect the hot water outlet pipe from your hot water heater.

      Pro Tip: Take the time to inspect the anode rod to see if it has suffered any extensive corrosion. This could also be one of the main causes of the bad odor. If it has been at least 3 years, it makes sense to replace the anode rod at the same time while you are in there.

      Note: A magnesium rod is considered higher quality for corrosion but can lead to odors as well. Aluminum or zinc are better options against smells as these metals are less likely to create odors in the future.

      Step 6: Add 3% Hydrogen Peroxide

      Now, this is where your high school chemistry lessons come in handy. You need to add in 1 or 2 pints of 3% hydrogen peroxide. This is the kind of hydrogen peroxide that you can buy at pretty much any drug store or even online. But, skip the baking soda! We are not trying to replicate the volcano eruption from the science fair.

      The idea is to put in 1 or 2 pints for every 40 gallons of your hot water heater tank capacity to disinfect the hydrogen sulfide. You can easily pour in the hydrogen peroxide through the hot water heater’s outlet pipe opening, whichever option you chose from the previous step.

      Step 7: Refill the Tank

      Once sealed back up, it’s time to fill your tank again. By reopening the cold water valve, fill your hot water heater with the amount of water you released. Be sure to monitor the water levels through any hot water faucet nearby. Close the inlet valve as soon as the tank is full. Let the hydrogen peroxide vapor sit in the tank for about 3 hours. This should leave you with a fresh water tank. See this post if you need more detailed instructions on how to fill a water heater.

      Step 8: Drain the Tank, Again

      After the 3 hours have elapsed, you need to drain the hot water heater tank again. Do this by opening up the cold water valve and all the hot water faucets in your home.

      This will drain the tank and allow the hydrogen peroxide mixture to go through the entire piping system, cleaning and ridding them of the stink in the process. Finalize this process by draining any remaining hydrogen peroxide solution through the heater drain valve.

      Step 9: Refill the Tank

      After draining the entire tank of the hydrogen peroxide mixture, it’s time to refill the tank, again. Simply make sure that the drain valve is closed and let freshwater run into the hot water heater tank. Once it’s full, let it sit for about 15 minutes.

      Step 10: Purge the Hot Water Heater of Air

      Purge your hot water heater lines of any air that might cause water pressure and flow issues. Do this by opening up the hot water faucets and closing them back up after all the air is out (it shouldn’t take more than a minute). They will sputter, and this is simply the air escaping.

      Step 11: Finish Up

      Finally, turn your water heater back on. You can use the manual electric switch or the gas control knob to “On,” depending on the kind of water heater you are using. See this post for turning on your electric water heater if you need more details.

      Check to ensure that your water heater is operating at normal capacity and that you didn’t adjust anything in the process.

      Once all this is done, it’s time to check for any water leaks at every single fitting that you touched. See a leak? Tighten as needed.

      See this post to troubleshoot leaks from either the top or bottom of the water heater.

      Summary:

      Although it might be a little tedious, you can clearly see that adding hydrogen peroxide to your hot water heater tank isn’t that complicated a procedure. Most homeowners can handle this one all on their own.

      If your smelly water problem originated from the tank, this homemade “sanitizer” will result in a fresh tank and should do the trick.

      Watch this video below to see the general process of adding hydrogen peroxide to your water heater:

      Final Thoughts: What if the Water Odor Problem Persists?

      This article primarily deals with eliminating smelly water coming from hot water. In many cases, adding hydrogen peroxide to the hot water heater tank by following the procedure laid out above should solve your rotten egg smell if it is hot water-based.

      However, in some cases, you will find that the problem persists for your hot water even after you thought you had fixed it. Here are some additional troubleshooting ideas if the smell continues.

      -Try replacing your standard magnesium anode rod with zinc or aluminum if you skipped this step above. If your water is particularly hard, try adding a powered anode rod for extra corrosion protection.

      -If you have a water softener, try also sanitizing at this source, particularly if water passes through it prior to reaching your water heater.

      Does only your cold water smell?

      If the source of the smell seems to be coming from your cold water only, the problem won’t be resolved by adding hydrogen peroxide to your water heater. Instead, you will need to address the water source. (Consider how much things like a chlorine odor are impacting your situation by asking your neighbors if they also deal with this.)

      Are You are on a Well and Have Smelly Water?

      Hydrogen sulfide is common in groundwater. Consider adding an additional water filtration system to deal with this and other anaerobic bacteria, manganese, iron bacteria, or additional causes. There are also sulfur kits that can be added right at the well itself by a well contractor. There are also lower-cost solutions you can add directly to the well.

      Caution: Be careful when considering chemicals or additives, such as potassium permanganate. These can pose health hazards, so you should always consult an expert.

      FAQ’s for Putting Hydrogen Peroxide in Your Hot Water Heater:

      How do I put hydrogen peroxide in my hot water heater?

      • Step 1: Turn Off the Water Heater
      • Step 2: Don’t Let Any Water In
      • Step 3: Relieve Tank Pressure
      • Step 4: Drain Some Water
      • Step 5: Disconnect Outlet Pipe
      • Step 6: Add 3% Hydrogen Peroxide
      • Step 7: Refill the Tank
      • Step 8: Drain the Tank, Again
      • Step 9: Refill the Tank
      • Step 10: Purge the Hot Water Heater of Air
      • Step 11: Finish Up

      Is it safe to drink water with hydrogen sulfide?

      While the smell and taste of hydrogen sulfide is unpleasant, it is generally considered safe to consume water containing it. Hydrogen sulfide gas can rise to toxic levels, but its presence in drinking water would have to rise to levels that would naturally prevent consumption before a health concern is presented.

      Why does only my hot water smell like sulfur?

      Hydrogen sulfide is a bacteria that is often present in water heater tanks. If only your hot water is smelly, but your cold water is odorless, your hot water contains this harmless bacteria that often smells like sulfur or rotten eggs.

      Can bacteria grow in a hot water heater?

      Yes, certain anaerobic bacteria thrive in containment where oxygen is not present. Not all of these bacteria are harmful, but they can produce odors and tastes in the water that are unpleasant.

      How do you get the smell out of a hot water heater?

      Yes, certain anaerobic bacteria thrive in containment where oxygen is not present. Not all of these bacteria are harmful, but they can produce odors and tastes in the water that are unpleasant.

      How do you sanitize a water heater?

      The easiest and most cost-effective way to sanitize a water heater is by adding hydrogen peroxide to the tank itself. Let it sit for at least 3 hours, and flush it out prior to using the water for your normal household activities.

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      I'm passionate about all things plumbing, and love sharing tips, "how-to", and reviewing the latest products to help make your project a success!

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