Why Does My Reverse Osmosis Water Smell Bad?
Written by: Gene Fitzgerald // Last Updated: Aug 8, 2023
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Reverse osmosis is supposed to eliminate any and all tastes and flavors from your water, especially the bad ones!
So, it can be pretty upsetting if your filtered water starts getting a little on the nose.
There are several reasons why your RO water might be a bit stinky, and we will look at them in more detail.
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Key Takeaways
Your RO water may develop a bad smell due to:
- Sulfur (hydrogen sulfide) in the source water
- Barium
- Chlorine/chloramine
- Algae, bacteria, or other biofilm which can also grow directly in your reverse osmosis system
- Other organic materials
- Old filters
Potential Reasons Why Your Reverse Osmosis Water Smells Bad
Identifying what is causing the bad smell in your RO water will help you find a way to fix it. Here are the main culprits that cause bad smells in RO water.
Sulfur (Hydrogen Sulfide) in the Source Water
If there is an odor in the water, it is likely due to hydrogen sulfide, which has a rotten egg smell. Activated carbon filters commonly found in reverse osmosis systems can eliminate some hydrogen sulfide at low concentrations. However, if the concentration is high, most of it will remain in the water.
Sulfur in different chemical forms behaves differently when it comes to water filtration. While sulfite and sulfate can be removed, hydrogen sulfide (a dissolved gas) cannot be filtered by reverse osmosis membranes due to its small molecular size.
Barium
Barium and cadmium are common contaminants found in water sources. Barium, often present in mineral ores, can seep into pipes and wells, resulting in a fishy smell. The EPA is responsible for managing barium levels in water to ensure they do not exceed the acceptable limit. Similarly, cadmium can infiltrate water through fertilizer and industrial waste contamination.
Now both barium and cadmium should be removed by a reverse osmosis system. However, if concentrations are too high, some of it will remain in the water.
Chlorine/Chloramine
Chloramine is formed by combining ammonia and chlorine. It serves as a disinfectant in public water sources to ensure water safety. However, the distinct smells of ammonia and chlorine combine to create chloramine, and its presence can contribute to the fishy smell detected in water.
Algae, Bacteria, or Other Biofilm
During the summer, bad smell in RO water may become more noticeable due to the prevalence of algae blooms. Algae thrive in warm water and sunlight, especially in reservoirs and lakes.
But algae can also accumulate and grow in your reverse osmosis system itself. The same goes for bacteria and other biofilm.
Other Organic Materials
RO water may develop an unpleasant odor due to the presence of organic materials in the source water.
Clogged Filters
A clogged filter element in your reverse osmosis system can grow all kinds of nasties and lead to bad smell in the permeate water.
How to Get Rid of Bad Smelling RO Water
Depending on what is causing the unpleasant smell of the RO water, there are several things you can try to fix it.
Flushing the RO System
The first and easiest thing to try is flushing the RO system. To flush your RO system, open the RO faucet and drain the storage tank, then let it refill and repeat the process.
Flushing Your Entire Plumbing System
If the above does not work, try flushing your entire plumbing system. Over time, all kinds of dirt can accumulate and cause clogs in your pipes.
Replacing RO Filter Elements
Over time, RO filters can deteriorate as contaminants and minerals accumulate. Following the RO filter and membrane replacement schedule is essential to avoid this.
If you have recently changed your filters and membranes, it is likely another issue causing the smell.
Adding a Carbon Post-Filter
Adding a carbon post-filter to your RO system can help to polish the water and remove any lingering tastes and odors.
Adding Pre-Treatment
If the water source has a lot of organic materials, sulfur, barium or cadmium, microorganisms, or chlorine/chloramine – more than your reverse osmosis system can handle – you can add pre-treatment to get rid of these.
- For example, you could use aeration to allow gasses like hydrogen sulfide to escape.
- Anion exchange also helps against sulfur smell.
- Bacteria can be eliminated using chlorine injection.
Calling Your Water Utility
If you are experiencing ongoing problems with unpleasant odors, contacting your water company to inspect your water source can help identify and resolve the issue. They have the expertise and resources to determine the underlying cause.
Is Reverse Osmosis Water That Smells Bad Safe to Drink?
Reverse osmosis water that smells bad may or may not be safe to drink, depending on what is causing the smell.
- For example, chlorination by-products can cause a chlorine smell, which in low concentrations may not pose any health risk.
- The same can be said for small concentrations of algae.
- However, if the smell is coming from something like high levels of barium, it could be dangerous to drink.
If you have any questions about reverse osmosis system smells please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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