Pentair 1,2,3-TCP Filter

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Opening: What Government Sampling Shows About 1,2,3-TCP in St. Mary’s County

The public water system serving parts of St. Mary’s County—Patuxent Naval Air Station (NAWCAD)—has undergone federal monitoring for 1,2,3-trichloropropane (1,2,3-TCP). Between 2014 and 2016, no results detected 1,2,3-TCP at or above the reporting threshold of 0.03 micrograms per liter (µg/L). This data reflects the system’s groundwater source and applies to the overall supplied water, not specific homes.

1. Why Aesthetic Secondary Standards Differ From Health-Based Limits for 1,2,3-TCP

Some water constituents, including 1,2,3-TCP, have secondary standards addressing taste, odor, or staining, which do not indicate health risks. For 1,2,3-TCP, health-based limits would stem from toxicity assessments, but at present, the Environmental Protection Agency (EPA) has not established a federal maximum contaminant level (MCL) for this chemical. Therefore, no violation or unsafe status is noted for any detection or lack thereof in St. Mary’s County public water.

2. Differences Between Public-System Records and Private-Well Testing

EPA monitoring data originate from regional public water systems, representing averaged conditions over multiple connections and through groundwater or surface sources. In contrast, testing a private well yields specific information about that water supply at the time of sampling. The absence of reported 1,2,3-TCP in the public system does not guarantee any individual private water source is free of it, emphasizing the need for private sampling when ownership or source conditions differ.

3. Understanding a Certified Laboratory Test Report for 1,2,3-TCP

A certified lab report for 1,2,3-TCP will specify the detection limit (often around 0.03 µg/L, as with the EPA’s survey) and the measured concentration, if present. A reported value below this detection limit or “non-detect” means that 1,2,3-TCP, if present, is at very low levels unmeasurable by that method. It does not imply the substance is absent, just below that threshold. Interpreting the report requires noting both the method detection limit and comparing results against any guidelines or standards relevant to health or aesthetics.

4. A Worked Example: Reading the Median and Range from the System Record as a Homeowner

According to the Patuxent NAWCAD system’s monitoring, all 20 samples for 1,2,3-TCP were non-detects. This results in a median of zero detections and no reported range above the detection limit. A homeowner using this data can understand that 1,2,3-TCP levels in the public supply were very low or undetectable during the survey period, supporting that this constituent was not a measurable concern in that system’s groundwater source at that time.

5. The Role of Plumbing Material and Age Separate From Source Water

Even when source water tests show low or no 1,2,3-TCP, household plumbing materials and age can affect water quality. Materials that leach chemicals or that contain residues from past water treatment could influence chemical detection at the tap. Such effects are different from the groundwater source quality and require separate evaluation if water test results show unexpected substances. Plumbing-related issues do not contribute to 1,2,3-TCP presence, which originates from environmental contamination at the water source.

6. Additional Questions for Commercial or Industrial Water Use

Commercial or industrial water users in St. Mary’s County might consider factors beyond household concerns, such as regulatory compliance for manufacturing processes or wastewater discharge limits. These concerns involve different thresholds, frequency of monitoring, and potential impacts on equipment. Residential users focus more on health, taste, and odor, while industrial operators consult specific regulations and operational standards, including any voluntary removal of 1,2,3-TCP to meet internal guidelines.

Closing: What Not to Conclude From the Area Data

Area-wide monitoring for 1,2,3-TCP in the public water supply shows no detectable levels above reporting limits but does not guarantee that any individual home’s water contains no 1,2,3-TCP. Private testing is the only way to determine specific household water quality. Also, the data do not identify any health-based violations or unsafe conditions in St. Mary’s County’s public system. Households weighing water treatment options can consider direct-purchase solutions like the Pentair 1,2,3-TCP Filter, which ships ready to configure and is designed to reduce this constituent if testing shows it present in their water supply.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2016-06-29. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR3 monitoring (2013-2015) for Patuxent Naval Air Station (NAWCAD) (MD0180022), MD: 20 results across 1 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level