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Hot Water Smells Like Rotten Eggs?

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

This common problem is the sign of a bigger issue that’s thankfully easy to diagnose and fix. So where does the water get that rotten egg smell and how do you fix it?

Why does my hot water have a sulfur smell?

Softened water can sometimes accumulate hydrogen sulfide gas, which gives off the offending “rotten egg” smell as it’s released. This smell can occur in cold water for a variety of reasons, but when it’s specific to hot water, your hot water heater is the most likely culprit.

Anode Rod

The anode rod is a component of your water heater that attracts corrosive agents in the water. As time passes, the anode corrodes, leaving the heater largely corrosion free in the process.

Sometimes this can lead to a reaction between the rod and sulfate from the water and the hot water stinks as a result. Some heaters have more than one anode rod, and it is important to check and replace them periodically to extend the lifespan of the tank.

Switching to a powered anode rod such as a Corro-Protec is often the easiest solution.

Sulfur Bacteria

A naturally occuring bacteria in the water supply can breed in your heater, leading to an increase in hydrogen sulfide gases. In this case, you will need to get rid of the bacteria in order to get rid of those water offending heater smells.

How do I fix it?

You can get rid of the rotten egg smell with a few simple steps. In the case of a bad anode rod, you will need to identify a damaged rod and replace it. For bacteria, hydrogen peroxide does a great job of cleaning the tank out and preventing the bacteria from breeding.

Diagnosing Your Anode Rod

As mentioned before, the anode rod is a “sacrificial” component which attracts corrosive elements. The warranty of most water heaters is thus tied directly to the number of anodes present, with one rod giving up to 6 years (12 years for 2). Normally, a rod is completely consumed within 4-5 years, although the rod can last up to 10 years or dissolve in only a couple years depending on your water quality and usage.

If you’ve never changed the anode rod before, you’d want to first lookup how old your water heater is.

To examine (and replace, if needed) your anode rod, you will want to have the following tools handy:

  • Garden hose (for draining)
  • Pipe wrench
  • Socket wrench
  • Thread sealing compound
  • A friend to hold the tank in place (if it isn’t anchored) to avoid pipe damage

Before attempting any work, be sure to turn off power to your heater. For electric heaters, this will be the circuit breaker in your fuse box that services the heater. For gas, you can simply turn the gas control valve down to the “vacation” setting or lowest setting instead of turning it completely off. The reason for this is that a heating element can be damaged if it comes into contact with air while in operation.

Turn off the cold water supply to your heater and connect the hose to the drain valve at the bottom of your tank. You can drain it into a bucket or drain, but be careful not to handle the hose, as it will be extremely hot during the draining process.

Next, locate the anode rod. It generally resembles a hexagonal plug and is usually at the top of the tank, but may sometimes be attached at the side. You will need to drain the hot water until it’s below a side-mounted rod (when at the top, the amount of water you need to drain could be as little as 1/2 gallon). Once the water level is low enough, turn off the drain valve and you can remove the hose once it’s cool to the touch.

Because there is now a vacuum in the tank, you will need to turn on a nearby hot water tap. This relieves the pressure inside the tank so that you can safely remove the rod. You will need your socket wrench for this, and may have to work the head a little to loosen it. It might also be necessary to tilt the rod as you remove it, if there’s not enough clearance.

A healthy rod may be too thick to remove. Looking at the rod, you will be able to see the amount of corrosion, and a bad anode will be mostly or fully eaten away.

Replacing an Anode Rod

Prior to replacing the anode rod, you may wish to consider replacing a bad one with a different type or material of anode rod.

Non-Traditional Anode Rod Types

Flexible anodes are the same as normal anode rods, except they are able to bend. This makes it easier to replace them in tight spaces.

Powered anode rods are a newer solution and emit electrical pulses that improve the rod’s anti-corrosive efficiency. You can also purchase hot water outlet rods to improve the existing rod’s efficiency.

Anode Rod Metals

There are three major metals used for rods, and you may wish to choose one that best suits your needs.

Zinc is naturally anti-fungal and will help limit the amount of bacterial growth in the tank. This will be the best choice if your water frequently ends up smelling. The most common zinc rods are actually a blend of aluminum, tin, and zinc.

Magnesium anode rods are the most common. They degrade faster, but work the best. As a bonus, the dissolved magnesium offers several health benefits. Pick this if you have less frequent occurrences of rotten egg smells in your water supply.

Aluminum anode rods corrode the slowest, and are cheapest. Chances are, this is the type of rod your heater came with. Because they are less effective than magnesium rods, these are best used if the rotten egg smell appears to simply be the result of a spent rod or you intend to flush with hydrogen peroxide occasionally.

How to Add Hydrogen Peroxide to Your Water Heater

Performing a 3 percent hydrogen peroxide flush will help get rid of anaerobic bacteria.

  1. Shut off the power as described above.
  2. Close the main shut-off valve.
  3. Open both a nearby hot water tap and the temperature and pressure relief (TPR) valve.
  4. Drain the tank until the water level is below the TPR valve, then shut both off.
  5. Add some 3 percent hydrogen peroxide(approximately 1-2 quarts per 40 gallons, adjusted to your tank’s capacity).
  6. Open the cold water intake valve until the tank’s filled.
  7. Shut the valve and go watch a movie.
  8. After a few hours, flush the tank by turning the cold water valve and hot water tap back on (this also treats your pipes).
  9. Allow the tank to refill as you normally would after a flush.
  10. If the water is cloudy or still smells, flush again.
  11. When the hot water taps are flowing normally, restore power to your tank.
author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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