Autotrol VOCs & Industrial Chemicals Filter

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Modesto’s Water System and Its Reach to Your Household

The City of Modesto in Stanislaus County, California, supplies water to over 218,000 people using surface water sources. This water undergoes treatment before distribution through more than 70,000 service connections. While this municipal water system serves a large and diverse population, it is important to understand the presence and behavior of volatile organic compounds (VOCs) within this system and how they might relate to your own household water.

How Gasoline Releases Differ from Dry-Cleaning Releases in Groundwater

VOCs encompass a broad family of solvent compounds with varying origins and chemical behaviors. For example, gasoline-related VOCs often include compounds like 1,1-dichloroethane and MTBE, which come from petroleum products and fuel leakage. Dry-cleaning solvents typically involve chlorinated compounds such as perchloroethylene or trichloroethylene, which are not specifically noted in Modesto’s water monitoring record.

Modesto’s public water system monitoring from 2013 to 2015 detected certain VOCs such as 1,1-dichloroethane and HCFC-22 (a refrigerant chemical), but no gasoline or dry-cleaning solvents were found above their respective reporting levels. This indicates the occasional presence of some volatile organics but does not confirm any ongoing source such as a fuel or dry-cleaning spill impacting the distribution system.

The Household Symptoms That May or May Not Indicate VOCs in Water

In the home, certain signs can suggest the presence of VOCs, including unusual tastes or odors in drinking water, staining on plumbing fixtures, or unexpected water discoloration. However, many VOCs are tasteless and odorless at low concentrations, and such sensory indicators are not reliable on their own.

Households often confuse common water quality issues with VOC presence. For example, chlorine taste or metallic flavors may arise from water treatment processes unrelated to volatile organics. The absence of obvious sensory symptoms does not guarantee the absence of VOCs, nor does their presence necessarily indicate a health concern.

Considerations for Large Households, Secondary Residences, or Seasonal Properties

Water usage patterns affect VOC exposure potential. Large households using higher volumes might experience different compound interaction due to flow and contact time in household plumbing compared to smaller residences. Seasonal or second homes might have stagnant water during vacancy periods, which can influence compound concentrations but does not inherently mean VOC contamination.

Water stored in plumbing for extended periods may accumulate VOCs if they are present in the supply. This stable water contact time can increase the efficiency of certain treatment approaches if used, but it also complicates detection without timely sampling.

Understanding 'Detected', 'Median', and 'Range' in Modesto’s VOC Sampling Records

The Environmental Protection Agency’s Unregulated Contaminant Monitoring Rule (UCMR3) results for Modesto list VOC detections over multiple sampling campaigns. Terms like 'detected' mean an instrument measured a compound above the reporting level, which is a threshold for reliable measurement, not a safety violation.

The 'median' of detections provides the middle value of all detected concentrations, while the 'range' indicates the variation from the lowest to the highest measurements found. For example, HCFC-22 was detected six times above the reporting level of 0.08 micrograms per liter (ppb), with a highest reading of 7.2 micrograms per liter and a median near 0.235 micrograms per liter. None of these results correspond to federal maximum contaminant levels (MCLs), as no such limits exist for these VOCs under UCMR3.

How VOCs Enter Groundwater or the Distribution System in Stanislaus County

In the Modesto area, surface water sources can receive VOCs from historic industrial activities, urban runoff, and atmospheric deposition. Although the public water system uses treatment methods to reduce contaminants, trace amounts of volatile organics can still be detected during routine monitoring.

Distribution system materials and plumbing infrastructure also influence VOC levels inside homes but do not create volatile organic compounds themselves. Understanding the pathways helps to identify whether detected VOCs originate in source water supplies or within household plumbing.

Testing to Clarify Your Household’s VOC Levels

The only way to determine the actual VOC levels in your own home’s water is to have a certified laboratory analyze a representative water sample from your tap. Such testing will quantify specific volatile organic compounds and provide data to decide whether targeted treatment is appropriate.

To address the presence of VOCs and industrial chemicals commonly found at low levels in the Modesto water system, systems like the Autotrol VOCs & Industrial Chemicals Filter can be purchased direct and configured for household use. This system uses granular activated carbon technology to reduce various solvent compounds effectively when sized properly for contact time with the water flow.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2014-02-06. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR3 monitoring (2013-2015) for City of Modesto (CA5010010), CA: 825 results across 7 listed contaminants, 8 detections above the reporting level; no federal MCL for these UCMR-listed VOCs