A common misconception about volatile organic compounds (VOCs) in residential water is that concentrations remain constant throughout the year. However, seasonal changes in the water table can move solvent plumes, leading to variations in detected VOC levels in the water supply. Understanding this dynamic helps households interpreting government data avoid misreading what fluctuating VOC presence means for their own water use.
How Seasonal Water-Table Changes Move a Solvent Plume Relative to a Well Screen
In the Mayaguez public water system serving Puerto Rico, solvent compounds—including VOCs—can be influenced by the water table’s seasonal rise and fall. When the water table fluctuates, the position of a dissolved solvent plume relative to the intake of a well changes. This movement affects the timing and concentration of VOCs measured at the system level, as groundwater flow shifts the plume nearer or farther away from the well's screened intake.
For households, this means VOC levels measured by government surveys such as the EPA’s Unregulated Contaminant Monitoring Rule (UCMR3) may vary seasonally. The EPA data showed, for example, detections of 1,1-dichloroethane in the Mayaguez water system ranging from 0.03 to 0.06 µg/L (micrograms per liter), or parts per billion, across multiple samples from 2013 to 2015. These fluctuations reflect regional groundwater conditions, not necessarily a consistent level at a particular home.
Why Volatility Matters: Showering, Dishwashing, and Inhalation Routes Versus Drinking
VOCs are volatile organics, meaning they readily vaporize into the air from water. This volatility is important because it influences how people may be exposed—inhalation during showering or dishwashing, as well as ingestion when drinking water. Unlike some dissolved contaminants that remain bound in water, volatile organics can enter air spaces within a home during common water use activities, increasing potential inhalation exposure.
Household equipment often addresses VOCs primarily for ingestion. When existing treatment systems can’t keep up, additional filtration may be required to reduce volatile organic compounds and solvent compounds to levels aligned with a household’s water use.
What the Measured Range Means Against the Relevant Federal Standard, and What It Does Not Mean
The EPA’s UCMR3 monitoring of Mayaguez water showed no federal Maximum Contaminant Level (MCL) exists for the detected volatile organics, including 1,1-dichloroethane and substances like chloromethane, bromomethane, and MTBE. Therefore, detections—even at the highest measured 0.06 µg/L for 1,1-dichloroethane—do not represent exceedances or violations. They are measurements used for ongoing evaluation and research.
It’s critical that households do not interpret these findings as indicating unsafe water or contamination. The system has zero EPA health-based violations recorded. Instead, these values show the presence of VOCs at trace levels, which may fluctuate seasonally and regionally.
How the Treated Water Differs at the Tap Once the Documented Technology Is in Place
The C-Series VOCs & Industrial Chemicals Filter is designed for households whose existing water treatment equipment cannot fully address volatile organic compounds detected in their area. This technology uses a contact-time-optimized carbon filter to reduce VOC levels effectively within the household water stream.
Once configured, the water delivered to tap fixtures will show a marked reduction in solvent compounds such as 1,1-dichloroethane, supporting safer and more comfortable use for drinking, cooking, and bathing compared to untreated or partially treated supply. Importantly, the system ships ready to configure for household use without requiring professional setup.
What 'Detected', 'Median', and 'Range' Mean in the Sampling Record on This Page
The EPA monitoring results reported 'detected' concentrations when instruments measured volatile organics above laboratory reporting levels. For example, of 52 samples for 1,1-dichloroethane, 2 were detected above 0.03 µg/L. The median of these detections was 0.055 µg/L, with a range from 0.03 to 0.06 µg/L.
'Detected' means the compound was measurable, not that it exceeds any health limit. 'Median' denotes the middle value of detections, providing a typical concentration among positive samples. 'Range' shows the spread between the lowest and highest detected levels, indicating variability in the environment.
How Many Samples and Wells Stand Behind the Figures, and What a Small Sample Means
The Mayaguez public water system’s EPA data includes 52 sampling results over multiple years for the volatile organics tested, reflecting multiple wells or points within the system. This sample size gives a broad overview rather than a precise measure of any single residential tap.
A smaller number of samples—as with MTBE testing where only 8 results were available—means less certainty about variation over time. Households should consider testing their own water to understand specific VOC levels locally, as system-wide data represents regional trends but not individual home conditions.
For household VOC management in Puerto Rico’s Mayaguez water system, the C-Series VOCs & Industrial Chemicals Filter provides a documented approach to address volatile organic compounds when existing equipment alone does not meet treatment needs. Its design aligns with daily water demand and the dynamic nature of solvent plume movement in groundwater.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2016-12-13. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Mayaguez (PR0003283), PR: 320 results across 7 listed contaminants, 2 detections above the reporting level; no federal MCL for these UCMR-listed VOCs