Diagnosing the source of hot water that smells like rotten eggs can be a frustrating experience. There are a few potential sources of this bad smell, and each source has a number of issues that could be causing the smell.
You may be wondering if the bad smell could be coming from your water heater. The most common cause of bad smelling hot water is anaerobic bacteria present inside your water heater. Anaerobic bacteria react with the sulfur, magnesium, and aluminum anode rods causing hydrogen sulfide gas which has a “rotten egg” smell in the hot water supply.
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The substance causing almost all bad smells in water is caused by hydrogen sulfide. There are a variety of ways in which hydrogen sulfide can get into your water supply ‒ your water heater is only one potential source. This article will discuss how hydrogen sulfide forms, the different ways it can get into your water supply, and what you can do to get rid of it.
Hydrogen sulfide causes rotten egg smell
If your water smells like rotten eggs, there’s a good chance your water heater is at least partially to blame. Anaerobic bacteria and sulfur in your water supply could be reacting with the magnesium or aluminum in your water heater’s sacrificial anode rod. This reaction will produce hydrogen sulfide gas, which emits the signature rotten egg odor.
Before you can effectively deal with a hydrogen sulfide problem, you need to understand where each of the components that make up the smell comes from.
The term “anaerobic bacteria” covers an enormous range of microorganisms that can exist in your water supply. For the sake of simplicity, we aren’t going to dive into specifics in this article. Just know that some types of bacteria that can live in your water are capable of interacting with sulfur and certain metals to make your water smell bad.
Sulfur in water is most often found in well water, as opposed to city or municipal water. The sulfur comes from sulfates that are present in the soil. When it rains, the groundwater that accumulates dissolves the sulfide ores and other minerals that contain sulfur. The water then enters your well water system, carrying the sulfur with it. Eventually, it makes its way into your water heater and reacts with the bacteria and metals, creating the signature rotten eggs smell.
The third component of the water that smells like rotten eggs is typically either aluminum or magnesium. These are the most common metals used in sacrificial anode rods, which are thin metal cylinders used in tank-type water heaters. When the anaerobic bacteria and sulfur react with one of these metals, hydrogen sulfide gas is produced and begins to make your water smell bad.
However, we need to determine whether or not the water heater is the actual source of the odor. To do that, we have a few simple tests to perform.
Find Where the Smelly Water is Coming From
Before you do anything, you need to figure out which part of your water system is causing your water to smell bad. While we’ve discussed how a water heater can produce a bad smell, there are a couple of other possibilities:
- The smell could be caused by bacteria from food, soap, or other substances that linger in your drain pipes.
- The smell could be caused by hydrogen sulfide coming in with your water source (before it ever hits your plumbing).
- The smell could be coming from inside the water heater due to a deteriorated anode rod.
To figure out the root source of the hydrogen sulfide, you can perform a relatively simple test.
The hydrogen sulfide source test
- Get a glass.
- Fill the glass with hot water from the faucet or water source that smells bad.
- Holding the glass, walk away from the faucet or water source.
- Smell the glass.
If the glass doesn’t smell bad, the source of the bad smell is probably the pipes directly below the water source. Bacteria from food particles, soap, or other substances have built up in the pipes. When you turn on the water, the gas shoots out of the pipes and permeates the air around the drain, which can make it seem like the water itself smells bad.
If the glass does smell bad, there are two potential hydrogen sulfide sources: your hot water heater, or the water supply itself. While you can certainly test your well to figure out if your water source is the cause, there’s a much easier and more immediate solution.
- Get a second glass.
- Fill it up with cold water this time.
- Smell the glass.
If the cold water smells, your water heater likely isn’t to blame, as cold water comes directly from your water source. If the cold water doesn’t smell though, you should assume the water heater is causing your water to smell bad.
Performing Your Water Heater Maintenance
Water heater maintenance is key to controlling bad smells in your hot water. As a water heater ages, sediment from the water supply collects on the internal water heater components and on the bottom of the water heater inner tank.
If your water heater is making a knocking sound, there is likely sediment buildup inside your water heater which can cause the liner in the inner tank to fail.
We have a detailed DIY guide to water heater maintenance in our article Water Heater Maintenance Tips to 2X Your Tanks Lifespan. We won’t get into all the steps here, but this guide provides step-by-step instructions on how to service and maintain your water heater.
Replace Your Water Heaters Anode Rod
The first option is to replace the water heater’s anode rod. Bad-smelling water that comes from the water heater is typically caused by a magnesium or aluminum anode rod. You’ll want to replace this with a rod made out of a zinc anode rod.
A zinc anode rod is actually an aluminum anode rod that contains one part zinc and 10 parts aluminum. The inclusion of zinc in the anode rod will greatly diminish the smell and should solve the problem.
There are some disadvantages though. A zinc anode rod is still sacrificial meaning it will need to be replaced periodically. Also, zinc anode rods are not recommended to be used if you have a water softening system.
Water softeners work by adding salt to the water supply to reduce the hardness of the water. Saltwater is very corrosive and will reduce the life of a zinc anode rod and eventually the life of the water heater itself.
Install a Zinc Anode Rod
If you need an anode rod that doesn’t make your water smell, A good choice is the About Fluid Aluminum/Zinc Flexible Anode Rod Complete Kit For Water Heaters. This segmented anode rod is made in part with zinc which helps control smelly water. This anode rod kit comes with everything you need, including step-by-step, easy-to-follow instructions and will fit most water heating units.
Powered Anode Rod Can Eliminate Smelly Hot Water
In my opinion, the best option to permanently remove smelly water in your water heater is to replace your current anode rod with a powered anode rod.
Powered anode rods use electrical pulses to remove corrosive electrons from the water supply and prevents it from attacking the water heater lining. Powered anode rods are not sacrificial and do not require replacement. So these powered anode rods can easily outlive the water heater itself.
Powered anode rods are the best option for controlling smelly water. They work by killing anaerobic bacteria in the water that leads to the water having a “rotten egg” smell. They use electric pulses to kill bacteria and remove corrosive minerals. Powered anode rods cost more than traditional anode rods, however, they are not sacrificial and will not deteriorate.
Our choice powered anode rods is Corro-Protec CP-R Water Heater Powered Titanium Anode Rod (40-89 Gallon Tank). This powered anode rod comes in 3 different sizes to fit the size of your water heater. The manufacturer states this anode rod will double the life expectancy of your water heater.
Check your water heaters data tag to be sure you’re buying an anode rod that will work with your water heater.
How to Replace the Anode Rod
To replace your anode rod, you will need the following tools:
- Garden hose (for draining)
- Pipe wrench
- Socket wrench
- Teflon Tape
- First, you will need to turn off the power to the water heater. For electric heaters, this will be at the service disconnect or the circuit breaker in your electrical box. For gas water heaters, turn the gas control valve down to the pilot or “vacation” setting.
- Turn off the cold water supply to your water heater. This is located on the cold water supply pipe coming into the water heater.
- Open the hot water tap at a nearby sink to release pressure on the line to allow water the drain from the tank.
- Connect a garden hose to the drain valve at the bottom of your water heater tank. Open the drain valve to drain the water to the exterior or into a floor drain. Be careful as the water exiting the hose will be extremely hot. Drain about 10% of the water from the tank.
- Locate and remove 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 hot water outlet.
- Install the new anode rod. Wrap Teflon tape in a clockwise motion around the threaded end of the anode rod to seal the connection.
- Close the drain valve and remove the garden hose.
- Close the hot water tap at the sink.
- Open the cold water valve to fill the water heater tank.
- As the tank fills, remove air from the supply lines by opening the hot water tap at the sink. Once all the air is released, close the hot water tap.
- Restore power back to the water heater. Turn the service disconnect or breaker back on for electric water heaters. For gas water heaters, turn the fuel valve back to the desired heat setting.
Replace Your Water Heater
If the anode rod has deteriorated so bad that it’s broken off or eaten completely away, the inner lining has likely become compromised and your only course of action is to replace the water heater.
Replacing a tank water heater is relatively easy and can be a do it yourself job if your are handy with tools and plumbing.
Consider replacing your water heater with a tankless water heater. Tankless water heaters can last about 20 years. Tankless water heaters will still require some routine maintenance, however, it will remove the bad smelling hot water.
Tankless hot water heater maintenance is different from tank water heater maintenance. Tankless units require flushing every few years to remove buildup on the burners. For more information on tankless water heater maintenance see Easy Maintenance Tips for Tankless Water Heaters w/Photos.
In a tankless water heater, hot water is not stored in a tank; rather it is produced on demand. Since there is no anode rod, heating elements, or steel tank to corrode, there is no hydrogen sulfide produced to cause the sulfur smell in your hot water.
See our Buyers Guide: What Tankless Water Heater Do I Need for more information on selecting the tankless water heater that is right for you.
Test Your Water Source
If your water source is the problem, it’s going to be a bit harder to fix. The sulfur is most likely seeping in through the groundwater that ends up in your well, and it’s not like you can replace the soil in which the sulfur is sitting.
Despite the increased complexity, there are a number of ways you can deal with excess hydrogen sulfide in your water source:
- Install a chlorine injection system.
- Install a peroxide injection system.
- Install a compressor tank aeration system.
- Install an ozone gas injection system.
The best way to determine which method to use is to conduct a mineral water analysis. Conducting this test and determining which desulfurization method to use is beyond the scope of this article, but you can use this excellent guide on treating sulfur odors in well water if you need some additional information.
This could result in having to replace some old galvanized supply piping and as a last result drilling a new deep well. The deeper the well, the better the water quality will be.
Competing Theories for Removing Smelly Water
Let me preference, I am in no way endorsing this theory however it does carry some degree of merit and may be worth considering. Let me explain.
There is a competing theory out there that states that you can remove the smelly water by just removing the anode rod from the water heater altogether and replacing the heating elements with stainless steel heating elements.
Water heater tanks have a thin glass lining over a steel tank. The anode rod, typically made of magnesium, reacts with minerals in the water supply creating the sulfur smell inside the water heater. The anode rod is there to protect the tank, however, removing the magnesium anode rod, in theory, removes the source of the smelly water problem.
The side effect of removing the rod altogether is your water heater elements will fail quicker. Since there is no anode rod to attack, the only thing left for the minerals in the water to attack is the tank itself and the heating elements. Since the elements are not lined, the elements will fail before the water heater tank does.
Where the typical water heater lasts 10-15 years, mostly because most people never replace the anode rod because they don’t even know it exists. By removing the anode rod, you can expect a reduced lifespan on the water heater of 6-10 years.
Ultimately, it’s my opinion that the best option for removing smelly water from a water heater is the powered anode rod. I’m not a fan of purchasing something as expensive as a water heater (a 50-gallon water heater averages about $600) with the inclination that it’ll end up in a landfill in 6 years. I’m all for taking whatever means are necessary to get the most use from it for as long as I can.
If you’re not inclined to invest in the powered anode rod, I would much rather replace a zinc anode rod every 1-3 years to protect the integrity of the water heater and my investment.
Ultimately, which option is best depends on you.
However, I do invite you to read the hundreds of 5-star reviews on Amazon for the Corro-Protec CP-R Water Heater Powered Titanium Anode Rod (40-89 Gallon Tank) from people just like you who had problems with smelly water. Water heater maintenance is something that most people will never perform unless a problem arises. For this reason alone, the powered anode rod is the best option.
If you are handy and are the type of person who will actively check and perform needed maintenance on your water heater, then the zinc anode rod is the best option for you.