What you’ll find on this page: We’ll tell you what causes rotten-egg odor. There are several situations, and we’ll help you figure out which one you’re suffering from. Then we’ll give you the solutions and you can decide which one is right for you.
What Causes Hot Water to Smell Like Rotten Eggs
The most common cause of smelly water is anaerobic bacteria that exist in some water and react with sulfur and the magnesium and aluminum sacrificial anodes that come with most water heaters to produce hydrogen sulfide gas, making the classic rotten egg odor. The problem is most common in well systems, either private or municipal.
Softening can make smelly water much worse. By the way, don’t blame the water heater manufacturers. It’s not their fault and it’s not their responsibility. It’s just a condition that exists in some parts of the country and each person has to deal with it.
What Not to Do to Get Rid of Smelly Water
We’ve heard of plumbers or handymen advising people to remove the sacrificial anodes from their water heaters as a solution to smelly water. It’s a solution all right, but one that will ensure that your water heater rusts out in record time. There is a reason why removing an anode voids all the manufacturers’ warranties.
Additionally, people have been told to replace a magnesium anode with an aluminum one. Don’t. Aluminum causes just as many rotten eggs as magnesium.
This Won’t Solve It Forever, But It’s a Start
Cheap, simple, effective, but not forever. Shut off the cold water valve to your water heater, open a hot faucet somewhere in your house to relieve pressure, drain some water from the tank, open the plumbing on one side, and dump in one pint of drugstore-strength hydrogen peroxide per 20 gallons.
Close everything up, turn on the cold water again, and let some water run from all spigots and taps. You should be odor-free for a week or two. Then you’ll have the problem again.
By the way: use peroxide, not chlorine bleach. Either will work, but peroxide is much safer.
And apropos to that: make sure it’s really the hot water that smells. There are places where there is so much sulfur in the water that hot AND cold water smell. Applying these procedures won’t solve that. But if the water smells like rotten eggs, then this solution will usually work.
The Complete Fix, in Most Cases …
Very often, replacing the standard magnesium or aluminum anode rod with an aluminum/zinc alloy anode will solve the problem. The zinc is a key ingredient, since pure aluminum anodes will also reek to high heaven. Also, some people use the terms aluminum and aluminum/zinc interchangeably. It’s important to be specific or you won’t solve the problem.
For most folks, an aluminum/zinc anode is the cheapest permanent fix for this problem and we suggest that you to try it first before considering the alternatives — unless you soften your water. More on that in a moment.
Contrary to our usual advice, we do not think you should put two anodes in your tank, even aluminum/zinc ones, as it may worsen the odor.
Some water heaters have two anodes. Not only is it important to put an aluminum/zinc anode into the heater; it’s also important to remove all previous anodes or the hot water will still smell.
If uncertain about what anode you have or which one to buy, consider paying for a consultation, or using our Anode Buying Guide.
… But, If You Have Softened Water
We have had people buy an aluminum/zinc anode and the odor didn’t go away. That’s vexing for them and us. A few were in unsoftened water, but most involved softened water. Softening can speed up anode consumption by increasing the conductivity of the water. That can increase the amount of hydrogen sulfide gas produced.
Some of these people thought that the anode had some secret ingredient that had been used up. This is NOT the case. If one aluminum/zinc anode fails to solve odor issues, the next one won’t do any better.
So we started offering powered anode rods. A sacrificial anode creates an electrical reaction inside a water heater as it corrodes. A powered anode does the same by feeding electricity into the tank. Since there is no magnesium or aluminum, there’s no smell. We don’t recommend them for everybody, though, because they’re several times more expensive than sacrificial anodes. But they are permanent: they aren’t sacrificial, so they don’t need replacement.
Another important point: powered anodes are not odor-eaters. They merely function to protect a water heater without creating any odor. So No. 1, don’t think it will fix anything other than rotten-egg odor that’s caused by bacteria reacting with sulfur in the water and the sacrificial anode that comes with the heater. And No. 2, if you buy one without checking with us and still have odor, let us know and we’ll troubleshoot and solve your problem. We’ve gotten pretty good at that.
One more thing: There are several configurations of residential water heaters. Use our consultation service to figure out which you have.
And worth mentioning again: Once in awhile aluminum/zinc anodes fail to resolve odor issues in unsoftened water, but mostly they work. It’s a little bit of a gamble. We could tell everybody to buy a powered anode, but they’re pricey. This is your choice, your gamble. Most people will win the bet, but it’s your decision.
Still, If You Have a Vacation Cabin… …
When a heater sits idle a long time, stagnation odor can develop and it’s different from anode odor and requires a different solution. Click here to learn about the Peroxide Fix.
If you’ve read all the information and are still not sure what you need, you can pay $40 for a consultation and I’ll get your details, scope out your situation, and make my recommendations. If you then buy a product from me within 10 days, I’ll refund it. — Randy Schuyler
Issues With Aluminum
In other parts of our site, we warn of issues with aluminum anodes. Those issues are exactly the same with aluminum/zinc anodes, which are about 92 percent aluminum. So if you install an aluminum/zinc anode, get in the habit of running the cold water for a few seconds before drinking it or cooking with it. That will flush out any aluminum-laden water from the water heater that has cooled off in the piping since the last use.
Regarding Stainless Steel Tanks
At least one manufacturer now offers a stainless steel water heater priced near to glass-lined steel tanks. We’ve been asked if that would be a viable solution to odor, since it doesn’t have an anode. The answer depends on whether you’re using a water softener. If you are, stay away from stainless, because saltwater is its bane and softeners add salt to the water.
We’re selling sacrificial and powered anodes and we think they are the most economical solutions. But they aren’t the only ones. One is Rheem’s Marathon electric heater, which is plastic-lined and has no anode. However, it costs several times more than a standard water heater and might be expensive to operate in some parts of the country where the utility rate structure favors gas.
Another is an instantaneous heater. We’re not overly fond of those. They cost several times more than a tank-type heater and have their own problems. To see what we think is the downside, consider reading Tankless. Still, this is one place where they might be a solution.
But Buyer Beware
A lot of people sell a lot of stuff and claim it will solve odor problems. If it doesn’t, you’ve spent money for nothing. One that has been touted in the past has been a chlorine injection system for wells. A newer one is a UV light disinfectant system. We cannot say these never work, but we’ve gotten a number of people coming to us and those systems didn’t work for them. And whatever you do, don’t drill another well! THAT’S been suggested, too.
Why Me, Oh Lord?
There have been a number of situations where people replaced their water heater and found they had smelly water with the new one even though they didn’t with the old one. All we can do is speculate on the causes. All the action in water heaters takes place where nobody can see and it never happens in a scientific laboratory testing environment.
It might be that toward the end of the life of a water heater, there was too little anode left to make much hydrogen sulfide gas. Or it might be the water supply changed in some way. Our own water heater once had smelly water and required an aluminum/zinc anode, and now it doesn’t.
There’s something few realize: water is a chemical and one that is constantly changing. The water that flows out of the tap this evening may be different from that from this morning, either because of what’s in the ground or because water companies have changed their sources of supply or added something new to it.