Evaluating Sulfur Smell Concerns in San Joaquin County Water Supplies

This week, you need to decide how to address the sulfur smell in your home's water supply, considering how it might differ if your household is large, a second home, or used seasonally.

Changes for Large, Seasonal, or Second Homes

Households with higher daily water use may find sulfur smells more noticeable since more water flows through fixtures and appliances. For seasonal or second homes, water sitting unused for extended periods can lead to stronger sulfur odors when the system is first used. These factors influence how noticeable the smell is but do not indicate higher sulfide levels in the groundwater itself.

Interpreting Sulfide Concentrations Against Federal Standards

Data from 15 groundwater samples taken from 14 wells in the San Joaquin County aquifer (S100CNRLVL) between January 2012 and June 2020 show sulfide was detected in 6 samples at concentrations ranging from 0.01 to 0.06 mg/L. The median sulfide concentration is 0.01 mg/L. None of these measurements exceed federal health-based thresholds. This means detection alone does not mean your water is unsafe or in violation of any law. These levels relate mostly to aesthetic concerns like sulfur smell rather than health risks.

Data Sample Size and Its Implications

The figures come from a limited set of wells drilled between 212 and 880 feet deep. While 15 samples provide insight into general conditions across the aquifer, the small dataset means local conditions can vary beyond this range. Your household’s water quality depends on your specific well or municipal source, so these figures serve as a regional guide rather than a definitive measure of your water.

Seasonal and Multi-Year Variation in Sulfide Levels

The sample dates span over eight years, from early 2012 to mid-2020, capturing seasonal and yearly fluctuations in sulfide concentrations. Variation within this period reveals sulfide presence is intermittent and can fluctuate, which aligns with common experiences of sulfur smell intensity changing with season or water usage patterns.

How Sulfide Enters Groundwater in San Joaquin County

Sulfide compounds typically form through natural processes involving sulfur-reducing bacteria reacting with organic material underground. In this region, such microbial activity in the aquifer contributes to the measured sulfide levels. The presence of sulfide in groundwater can also lead to hydrogen sulfide gas, which produces the characteristic rotten-egg sulfur smell when water is exposed to air in your plumbing.

To determine your household’s specific sulfide level, you should order a certified laboratory test of your well or tap water. A result showing sulfide at or above the area median would confirm the source of the sulfur smell. If sulfide is present at levels causing nuisance odors, the C-Series Rotten-Egg Sulfur Smell Filter ships ready to configure as an effective treatment option to reduce those odors and improve your water experience.

Where this information comes from

Source: USGS groundwater sampling. Sampled 2020-06-16. These figures describe groundwater sampled in this area. They are not a test of any individual private well - only a test of that well can establish its own water.

On record: U.S. Geological Survey sampling of Sulfide in the S100CNRLVL aquifer (San Joaquin County): 15 results from 14 wells, median 0.01 mg/L, range 0.01-0.06 mg/L; none above any federal threshold