Unpleasant Sulfur Rotten Egg Odor in Water

Water which smells musty or like rotten eggs is off-putting and often embarrassing for homeowners. Here you’ll find a guide on causes so you can confidently identify your smelly water problem.

Determining if your water has a sulfur problem is almost always made through observation since available testing must be done on site with sophisticated equipment. Often, we’ll ask customers to find a spigot as close as possible to the water source, draw some water into a clear glass and look for two indicators. Does the water have the smell? Does the water appear opaque then clear up with time as if there were tiny bubble in it? The fact you smell the rotten egg odor is as good as any test to tell us it is present, and treatment is necessary. Most common comparisons for smell are propane gas, rotten eggs, or geothermal vents like geysers.

The Root Cause: Hydrogen Sulfide Gas Production

That nasty smelling rotten egg odor is often a result of bacteria producing hydrogen sulfide gas. Even minute amounts of H2S can be enough to ruin your otherwise perfect water and may be strong enough you can't even take a shower or be in the same room as running water.

Treating Hydrogen Sulfide: A Prerequisite to Other Treatments

If you’ve got H2S it must be treated, or it will cause other water treatment to fail as it coats filter media preventing the media from working as designed. If you want to see the full advantage of other water treatment you will have to treat the H2S problem.

Steps to solve the rotten egg odor in water 

1. Plumbing Work: (You may want to have a plumber do this for you) 

• Check your untreated water to see if the problem exists. If it does not, then the odor causing bacteria are finding food in your plumbing system. If it does, the root of the problem is with your supply. 
• Check any filters you might have. Look for a cellulose based (usually pleated) filter and if found remove it from the system and replace it with a non-cellulose filter. H2S bacteria are known to eat and thrive off cellulose filter material. 
• Determine if the odor is on the hot water side only or if on both cold and hot. 
• If on the hot side only you might be able to mitigate the problem by replacing your factory hot water tank anode with an aluminum / zinc anode. 
• After removing any cellulose based filters and swapping out your hot water heater anode the next step is to chlorinate your plumbing to kill the bacteria. This might need to be done several times as the goal is to kill the bacteria. These bacteria can hide in exceedingly small places inside your plumbing and if not killed the first time they will reproduce to the point of causing the odor to re-appear. Repeat chlorination is common. 

2. Chlorinating to disinfect your plumbing

Disinfection is not a complicated process and the steps go like this: 

• Flush hot water tank till water runs clear. 
• Turn off your water and remove existing filters from your treatment system. 
• Clean your filter housings and add about a cup of bleach to the first housing and reinstall both housings. 

Cold Water: 

• Go to the furthest water tap, turn it on and let it run until you smell chlorine. 
• Go to the next furthest water tap and repeat until chlorine odor is detected at every tap. If you need to add chlorine to the filter sump again to get the odor at a tap do so. 
• Let the system sit with chlorine for several hours then flush. 
• Start with the furthest water tap and work your way back to the last tap flushing until you no longer smell chlorine. 

Hot Water: 

• Repeat above process running hot water 
• After allowing chlorine to work for several hours flush all lines. 
• Start with the furthest water tap and work your way back to the last tap flushing until you no longer smell chlorine. 

Repeat all above steps at first notice odor is re-appearing. 

3. Specialized Hydrogen Sulfide Water Treatment Systems: 

• Assuming the odor is not too terribly bad (you can still take a shower). 
• You will need to add a ICS-H to your treatment system to address the H2S problem and protect downstream treatment. 
• Repeat chlorinating process. 
• Replace existing downstream filters 
• Assuming the odor is terrible (you cannot take a shower or not even able to be in the same room as running water). Or the ICS-H just does not take care of all the odor. 
• You will need to add an additional ICS-H or backwashing oxidizing filter. 
• Repeat chlorinating process. 
• Replace existing downstream filters 

Key Precautions:

If your existing filters have been compromised with hydrogen sulfide do not replace them before you have addressed the problem. Left untreated will cause premature failure of existing treatment.

Conclusion: A Fresh State to Your Water Supply

Unpleasant smells in water, often likened to sulfur or rotten eggs, can be a source of distress. By identifying the root cause and taking diligent steps to treat the issue, homeowners can regain control over their water supply.