Hot Water Smells Like Rotten Eggs?

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There’s nothing worse than coming home from a rough day at work, drawing a tub of nice hot water to soak in, and walking back into the bathroom to a terrible sulfur smell coming from the hot water.

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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.

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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.

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Comments

  1. Hai, we were facing lot bad smell in our hot water.and we don’t know how to solve this problem. and this is big project here we have more than 25 areas same as we facing this problem

    Reply
  2. I read somewhere that there is a piece u can buy to put on ur electric hot water heater that will help eliminate the smell but now i can’t find the article. Do u have any idea whet the piece is called

    Reply
  3. We purchased a new hot water tank and the smell was immediate, after lengthy investigation it was a faulty hot water tank, as when it was replaced no smell.

    Reply
    • I’m having the same issue with a brand new Rheem water heater. It was only installed about 2 weeks before I started to smell the sulfur odor. Did you have it replaced with warranty by the company that installed it?

      Reply
  4. OK but what is a “TPR valve”? You don’t explain at all on this page…
    So I found it is the “Temperature/Pressure Relief” valve. It would be good to describe this before writing instructions, eh?

    Reply
    • You’re correct, it’s the temperature and pressure relief valve. I always try to provide the full name before using the acronym but missed this one. It’s fixed now.

      Reply
  5. We had the rod replaced in the hot water tank but after a few months the smell is back. We have a water filtration system to. Any suggestions as to what is causing this? This is a new home.

    Reply
    • We have the same problem! Just moved into our new (30 year old) home that’s on a well system. The water smelled like burning metals and had a lot of black crud coming out of the faucets. We did everything that we could think of, including changing the filter four times in 6 months, added water softener as recommended, and nothing changed. We noticed that the old water heater was mfg’d. In 1985, and was 34 years old. So, we bought and replaced the old with a brand new one, and we flushed the pipes for several hours. Today, 4 days later, the hot water smells like rotten eggs … even with a brand new water heater, and water softener and filter. What gives?

      Reply
      • We have the same problem! Replaced our gas water heater 5 weeks ago, we have well water,we have a water softener and only hot water smells! Smell started 3 days ago

        Reply
      • Its probably in your well water. You may need to shock the well or use a whole house carbon filter to remove smell.

        Reply
  6. Hi. I just moved into this house a month ago. We bought a Rheem water heater. We also have a whole house filter. for the first week or two, there were no issues and the water was perfect. However, there is now a heavy rotten egg smell. What can be causing this? It is in the hot water mainly, but will occasionally be in the cold water from what I assume to be the hot water coming into the cold. It’s the worst when we haven’t used it all day or wake up in the morning.

    Reply
    • I also must note that the water outside is sulfur water. However, the filter we bought filters out smell, so I doubt it’s coming from outside.

      Reply
      • If the water heater is new, an old anode rod wouldn’t be the issue so the source is somewhere else. Did you notice the smell prior to the new water heater? I would first check the condition of the whole house filter(s). It may simply need a new cartridge.

        Reply
      • Heating the water can make existing traces of sulfur odor from the incoming cold water worse.
        Make sure your “filter” for the Sulfur is working properly. Consider hydrogen peroxide injection in addition to your filter.

        Reply
  7. We have two hot water heaters. One gas, one electric. The hot water that comes through the electric hot water heater smells awful. Is it common for only an electric water heater to be the problem?

    Reply
  8. I bought a Kenmore 40 gal. electric water heaters from Sears. Within 2 weeks there was a bad rotten egg smell to the hot water. Took the anode rod out, added bleach down the hole and put in a zinc/aluminum anode rod replacement. Refilled it and let it sit overnight. Next day flushed the heater 3 times. Haven’t have a problem since.

    Reply
  9. Really hoping someone can help me. My water heater is less than two years old. Started noticing the rotten egg smell, mainly upstairs, a couple months ago. Water company came out and said water tested normal. Plumber came out and determined it was the anode rod in the water heater, so he replaced it, drained some water from the tank, added peroxide, and refilled it. Initially I thought that worked, but within a couple days, the smell was back. I tried turning up the heat on the water heater. Plumber came back out a week later and put another brand new rod in (I believe he said the new one was more zinc) and added two more quarts of peroxide. It’s been several days and the water still smells. Again, primarily upstairs (all taps) and notice it as soon as you turn the water on (when it’s still cold). I’m at a loss as to what to do next. Plumber says I may need a completely new water heater, which is a blow considering I just put this one in less than two years ago. So again, any help would be greatly appreciated!

    Reply

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