A rotten egg smell in well water is hydrogen sulfide gas. It usually comes from the aquifer itself (common in deeper Trinity and Paluxy wells), from sulfur bacteria in the well or plumbing, or from a water heater's anode rod reacting with the water. If only the hot water smells, suspect the water heater. If both hot and cold smell, it's the well.
Water Well Drilling Weatherford tests and treats Parker County wells with a rotten egg smell in well water more often than almost any other complaint. The good news is that the cause is usually one of three things, and a simple test narrows it down before anyone sells you equipment.
Step 1: The hot-versus-cold test
Run cold water from a tap that bypasses any softener or filter (an outside hose bib is ideal), then run the hot water.
- Only the hot smells. The water heater is the likely source. Magnesium anode rods react with sulfate and bacteria to produce hydrogen sulfide. Swapping the anode, and flushing and disinfecting the heater, often fixes it.
- Both hot and cold smell. The sulfide is coming from the well or the aquifer.
- Smell is strongest when water first runs, then fades. Often sulfur bacteria in the well or plumbing. Shock chlorination and a bacteria test are the next steps.
- Smell only after the softener or filter. Bacteria may be growing in the treatment equipment itself.
Step 2: Why Parker County wells smell
Hydrogen sulfide is common in deeper Trinity aquifer and Paluxy wells in North Texas. It’s produced naturally where groundwater sits away from oxygen in contact with sulfur-bearing minerals or organic material. A deeper well, like many east of Weatherford and around Aledo and Granbury, is more likely to carry it. Sulfur-reducing bacteria in a well or pressure tank can produce the same smell even when the aquifer water is clean.
Step 3: Test before you treat
A lab test for hydrogen sulfide, iron, manganese, pH and bacteria sets the treatment. The strength of the sulfide matters most:
- Low levels: catalytic carbon filtration.
- Moderate to high levels: air injection, where air oxidizes the sulfide inside a filter tank, or chlorine injection with a contact tank and carbon to remove leftover chlorine.
- Bacterial source: shock chlorination of the well and plumbing, then a retest. Add continuous treatment if it comes back.
Iron often travels with sulfide in Trinity water and changes the design, so both get treated in the same train, ahead of any softener. See iron filter vs water softener.
What it costs
An iron or sulfur system typically runs $2,000–$4,000 installed. A water heater anode swap costs far less. See well water filtration system cost and well water filtration.
Bottom line
Run the hot-versus-cold test first. Hot only points to the water heater. Both hot and cold point to the well. Then get a lab test for sulfide, iron and bacteria before buying treatment, because the right fix depends on how strong the sulfide is and what's causing it.
Questions about your own well? Call (817) 382-3840. A person answers 24/7.
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