The U.S. Geological Survey sampled groundwater in the San Joaquin County aquifer, measuring sulfide concentrations in nine wells ranging from 60 to 330 feet deep between July 2019 and April 2023. Sulfide was detected in four samples with a median of 0.03 mg/L and values from 0.01 to 0.08 mg/L, all below federal standards.
Understanding These Sulfide Measurements and Federal Standards
Each detection of sulfide in this area’s aquifer was well under any federal threshold for drinking water, indicating no health-based violation for this constituent during the sampling period. However, these values show a level of sulfide that can cause sulfur odor, commonly described as a rotten-egg smell. Importantly, detection at these concentrations does not itself confirm the presence or absence of a problem in any individual household’s water supply, as only testing of that specific water provides confirmation.
Household Signs That Relate to Sulfur Smell—and What Doesn’t
Residents experiencing a sulfur odor often report the water’s smell turning noticeably like rotten eggs when drawn at taps or showers. This foul odor may affect water taste and usability but is not necessarily accompanied by other symptoms such as visible water discoloration or taste deviations unrelated to sulfur. If your previous treatment for sulfur smell has failed, persistent odor despite treatment may indicate the need for a different or refreshed approach to filtration.
Seasonal and Multi-Year Patterns Seen in the Sulfide Data
The data span nearly four years, from mid-2019 to early 2023, showing sulfide detections occurred intermittently rather than constantly. This pattern suggests that sulfide levels in San Joaquin groundwater can fluctuate over time, potentially influenced by environmental factors or well characteristics. These variations underscore the importance of ongoing local water testing to determine current conditions rather than relying solely on historical area data.
Matching Treatment Capacity to Your Household Demand
Effective management of sulfur smell requires treatment equipment with capacity aligned to the volume of water your household uses daily. Treatment systems optimized for residential use handle typical household flow rates and water withdrawal amounts efficiently. When existing equipment fails to control sulfur odor, it may lack adequate capacity or require replacement with a system designed to address the specific chemistry of San Joaquin County’s groundwater sulfur compounds.
Expectations Based on Well and Sample Depth
The sampled wells vary between 60 and 330 feet deep, reflecting different groundwater strata within the San Joaquin aquifer. Sulfide presence can vary with depth due to geological and chemical factors. If your water is drawn from a deeper or shallower source than those sampled, sulfide levels—and thus sulfur odor intensity—may differ from the area’s median values. Recognizing your well depth helps set realistic expectations for treatment needs.
Important: Area sulfide data from these government samples indicate general conditions in San Joaquin County’s aquifer but do not establish your household’s water quality. Only a certified laboratory test of your specific water supply can determine your water’s sulfide concentration and confirm whether treatment is necessary. For households experiencing persistent sulfur smell with failed previous treatment, the C-Series Rotten-Egg Sulfur Smell Filter ships ready to configure and offers a documented solution designed for residential water systems addressing these sulfur odors.
Where this information comes from
Source: USGS groundwater sampling. Sampled 2023-04-20. 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 aquifer (San Joaquin County): 9 results from 9 wells, median 0.03 mg/L, range 0.01-0.08 mg/L; none above any federal threshold