Once in a very great while, we’ll hear a customer complain that their hot water smells like rotten eggs. Weird right? Well, yes and no. It sounds strange, but there’s actually a scientific explanation for the cause. Now, a scientific explanation doesn’t make bathing in rotten-egg water any more appealing, but here’s the cause and some solutions.
First, the Scientific Explanation of the Rotten Egg Smell
We should begin by mentioning that smelly hot water is actually very rare for commercial water heaters these days. Residential heaters still experience this phenomenon more often…But it’s worth exploring this question, especially if you notice a change in your commercial hot water.
First of all, it’s important to make sure that the smell is actually coming from your hot water (and not the drain or another area near the faucet). If you notice a distinct rotten egg odor from the hot water itself, that’s when it’s time to do some science exploration.
The rotten egg odor in hot water is caused by non-toxic sulfate-reducing bacteria (SRB), scientifically known as desulfovibrio. While that may sound alarming, the bacteria is harmless. All water contains some bacteria, which are either harmless or in too low concentrations to be of concern—harmful bacteria are removed during the treatment process.
The presence of SRB alone doesn’t result in smelly water. These bacterial strains require very specific conditions to survive and produce the “bad gas smell.” They require oxygen-deficient water (such as that found in deep wells and plumbing systems) with an excessive amount of sulfur. The water cannot exceed 138°F and needs direct contact with activated oxygen.
These bacteria feed off the sulfur naturally present in many groundwater supplies. When the sulfur feeding process occurs in environments containing hydrogen, it results in hydrogen sulfide gas—and that’s why your hot water stinks.
We can think of this loosely like the human breathing process—we get energy from breathing oxygen, but when the oxygen is converted to energy, our carbon-based bodies exhale carbon dioxide.
But Why Does Only the Hot Water Stink?
Water is a chemical compound, and as a result, it can alter and be altered by various elemental factors—especially heat. When water comes into contact with certain metals, the oxygen reacts with the metal, creating new compounds; some of these compounds have corrosive properties that eat away the metal surfaces over time.
Some metals corrode faster than others, so when two metals are placed together in water, the weaker of the two will attract the corrosive elements (keeping the stronger metal safe until the weaker metal has completely corroded away).
For that reason, all water heaters come equipped with an anode rod, typically made of magnesium or aluminum. Sometimes, these are called “sacrificial anodes” because the rod is sacrificed to protect the heater’s steel tank from premature rusting. When magnesium comes in contact with hot water, separate activated hydrogen molecules sit on the metal surface. In healthy water environments, this is a sign the anode rod is doing its job. However, in water containing SRB and high levels of sulfur, the reaction gives the final ingredient for the bacteria to thrive—activated hydrogen.
Manufacturers have improved commercial water heaters over the years. Most of them are now equipped with powered anode rods. These rods emit a light electrical current, which prevents corrosive materials from adhering to any metal inside the water heater tank. These powered rods avoid the chemical reaction that causes smelly water, making it a pretty rare problem in commercial settings. This is a far more common occurrence in residential water heaters, because they are typically still equipped with basic metal anode rods.
To some, the solution seems pretty simple—remove the anode rod to eliminate the hydrogen, and the smelly water is resolved, right? No. Technically, the smell may be eliminated, but that won’t actually eliminate the bacteria, which is the root cause of the problem. Instead, removing the rod will cause rapid corrosion of the steel tank of your water heater, causing premature failure and also voiding your warranty!
So then the solution seems to be to turn the water heater temperature up above 140°F to kill the bacteria. While this could be a solution, the high temperature can cause severe burns on human skin rather quickly, with just 3 seconds of exposure causing 1st-degree burns and 5 seconds causing 3rd-degree burns. So, while this solution may work in your home (although we wouldn’t recommend it), it won’t work in commercial settings with multiple end users. If you believe you can keep your residential water at 140°F and avoid injury, then this temp would prevent the bacteria from surviving in the water heater, but it would still require you to disinfect the water heater upfront.
How to Get Rid of the Rotten Egg Smell
First of all, if you notice a rotten egg smell, you should contact your commercial water heater professionals at Reliable Water Services. We can help you pinpoint the problem and figure out a solution that will keep your business (and your water heater) in good health.
The process of getting rid of the smell begins with disinfecting the water heater and the hot water lines (or the well, if applicable) to kill the bacteria. This process involves flushing the water heater with peroxide to kill the bacteria chemically or using a high-temperature shock treatment to disinfect the system. We like the high-temperature method because it doesn’t require adding more chemicals to an already messy water system. BUT keep in mind this can be extremely dangerous if not done correctly, so it’s important to call and hire a trained professional.
Unfortunately, both methods are only temporary until more SRB return and multiply. So, over time, you may need to repeat the process—the frequency varies depending on how much bacteria is in the water supply. For well water, treatment at the source is an option if you can bring in an expert to do a shock chlorination treatment of the well. As you can imagine, this process is often costly and still doesn’t prevent SRB from returning to the well in the future.
If you suddenly notice smelly hot water and you’re on a municipal water system, the bacteria often stems from nearby construction hitting a line or another temporary factor. Municipal water is chlorinated and treated at the source, but due to damage, supply lines can become exposed to ground elements.
For long-term solutions, it’s likely time to update to some more advanced technology. The magnesium or aluminum anodes in the hot water heater need to be replaced with a powered anode rod, which eliminates the chemical reaction with the bacteria (and the accompanying smell). But adding an anode rod is absolutely a job for a professional plumber. You need to get the right size, and it must be correctly installed to retrofit into the water heater’s existing electrical wiring (even on gas models). We all know electricity and water don’t mix, so safety is critical—leave it to the pros.
Even replacing the anode with a different type of metal (aluminum alloy or zinc) after disinfecting the water system can work. Replacing the anode with a less reactive metal like zinc will reduce the amount of hydrogen extracted and give the new bacteria less to work with while still protecting the tank. The downside is that the anodes will corrode quickly, so they must be checked and replaced often. If you have softened water, this solution won’t do much for you either—the sodium in softened water causes the same reaction as the metals.
More Permanent Solutions for Smelly Water
More permanent solutions entail eliminating the bacteria in your well water system with a chlorination feed line to treat all water entering the building. This solution completely prevents the bacteria from reaching the water heater. Chlorination units that use chlorine pellets can be installed directly at the well but require pre-approval from the DNR.
There are units you can install on the water line leading into the building that treat with liquid chlorine. However, installing any chlorine system is costly and means that you’re adding a constant chemical treatment to your water (which is not ideal). Often, this method requires the user to install another filter to remove the excess chlorine from drinking water. So we like to suggest the other, less pricy options before going down this road.
Another permanent solution to smelly water is to replace your existing water heater with one that features a glass-lined or stainless-steel tank. Both materials are naturally corrosion-resistant and don’t require anode rods. Of course, this option should be considered if it’s time to upgrade your water heater anyway—the replacement will likely involve a model change and can be costly.
To solve the smelly hot water issue in the long term, you may need to troubleshoot a variety of these potential solutions. Every case is different, so it’s hard to know which solution is the solution to your specific issue. Most people prefer to start with cost-effective options first and then go up from there.
One thing is for certain: if you have an issue with your commercial water heater, reach out to Reliable Water Services. Our trained professionals can help you resolve commercial water heater problems so you and your customers don’t have to deal with water that’s less-than-perfect. Reach out today at 1-800-356-1444!
