How To Add Hydrogen Peroxide To Water Heater

How To Add Hydrogen Peroxide To Water Heater

An offensive odor from cold water could be caused by contamination in your water supply. But if your heated water starts to smell like sewage, it is probably due to pollution caused by reactions in your heating system.

Here you will learn how to add hydrogen peroxide to your water heater to help take care of the contamination and nasty rotten egg smell that may be invading your nostrils. Simply turn off the water heater, drain the tank, and add your hydrogen peroxide.

Read on for more detailed steps when learning how to add hydrogen peroxide to water heater.

Steps To Add Hydrogen Peroxide To A Water Heater

Here is how to add hydrogen peroxide to a water heater.

Step 1: Turn off the hot water heater

Turning off the hot water heater is a pretty basic step, but it is also necessary as a safety precaution. Also, you don’t need the heater to heat water while working on the appliance, so turn it off to reduce energy consumption.

Step 2: Drain the water heater tank

Next, you need to drain the water from the tank completely. Before you remove the water, make sure it is cool enough to prevent accidental scalding.

To drain the water from the water system:

  • Open the drainage valve and allow the water to drain completely
  • As the tank is nearing empty, you will likely notice residue in the water. Allow some cold water to enter the tank to help flush all sediments
  • Continue to drain the tank until the water coming from the outlet is clear and without residue or deposits

Step 3: Observe the anode

Nearly all water heaters feature anode rods that produce excess ions during a cathode-anode reaction. In many cases, the anode rod is the main culprit for the foul odor because it absorbs most of the microorganisms and attracts the corrosive agents in the water to itself.  

The anode rod starts to emit an unbearable smell once it wears off. Inspect the anode rod for signs of wear. If it looks as if it has been eaten up by bacteria, it is time to replace it with a new aluminum/zinc anode rod.

Step 4: Measure your hydrogen peroxide

For your hydrogen peroxide treatment, you need one to two pints of 3% hydrogen peroxide for every 40-gallon capacity tank. Make sure to measure the correct quantity of hydrogen peroxide for your water heater tank capacity. You can find hydrogen peroxide in most drug stores and online.

Step 5: Add hydrogen peroxide to the tank

Now, it is time to add the hydrogen peroxide to the water heater tank. To do this:

  • Make sure the water heater’s outlet is closed
  • Pour the hydrogen peroxide into the empty water heater tank

Step 6: Fill the tank with cold water

With the correct quantity of hydrogen peroxide added to the tank, do the following:

  • Open the cold-water inlet of the heater
  • Fill the tank with cold water, making sure to observe the water level
  • Once the tank is full, close the inlet valve
hydrogen peroxide in water heater
Source: Matius

Step 7: Allow the water and hydrogen peroxide to mix

There is nothing for you to do at this stage besides wait. Do not turn on the heater just yet. Simply allow the water to seep into the hydrogen peroxide for about two to three hours. This will allow the peroxide mixture to counter the offensive odor.

Step 8: Flush the tank

Do the following after about three hours of your hydrogen peroxide treatment:

  • Open the cold water valve and the hot water faucet, and then flush the tank. This should clean both the tank and the pipes
  • Close the heat drain valve and fill the tank with clean water
  • Allow the water to sit in the tank for about 15 to 20 minutes
  • Flush the hot water tank again, making sure to purge the supply pipes and removing any sediments
  • Continue to flush the hot water tank until the foul smell is completely gone
  • Keep an eye out for any leaks during the flushing process, and effect necessary repairs

Step 9: Fill up the hot water tank

Once you can no longer detect the foul odor, close the outlet, and fill the water heater with fresh water.

Step 10: Turn on the water heater

Now, turn on the water heater and enjoy your fresh hot water supply.


Now that we’ve seen how to add hydrogen peroxide to a water heater, it is important to be sure that the foul smell is actually from the water heater before treating the appliance. If the bad smell is coming from your other water outlets, you are probably dealing with a hydrogen sulfide problem from your main water source.

Adding hydrogen peroxide to your water heater will only take care of any contamination in the tank caused by microorganisms and sediments. By draining the tank, adding the peroxide mixture, allowing it to sit for a couple of hours, you should have fresh-smelling hot water for your home use.

Frequently Asked Questions

How Often Should You Clean a Water Heater?

Here’s a straightforward answer: as frequently as the foul odor is perceived. But if you follow the steps in this guide, you shouldn’t have any reason to clean your water heater more than once a year.

Sulfide gas from sulfur bacteria can give water a rotten egg odor or foul smell. Unfortunately, the bacteria can thrive in hot water tanks, especially when it is left for an extended period.

Cleaning the water heater clears the tank of the bacteria and removes sediments that cause corrosion in the tank.

Is Hydrogen Peroxide Safe?

Treating water with hydrogen peroxide is considered a safer option than many other alternatives. This is not merely because it is a strong disinfectant but also because it doesn’t pose the kind of health and environmental risks associated with other types of disinfectants.

Using hydrogen peroxide to disinfect water is generally considered safe in low doses. In contrast, chlorination – a popular water disinfection method – may be associated with the risk of carcinogenic activities in humans.

What Are the Benefits of Adding Hydrogen Peroxide to Water Heater?

There are so many benefits of treating water with hydrogen peroxide. These include working faster than chlorine, preventing bacterial slime, and removing hydrogen sulfide – this compound leads to corrosion of plumbing systems. Hydrogen peroxide also integrates into water immediately, and it is biodegradable.