This week, households in Roanoke City face a decision between two technical approaches to manage 1,2,3-trichloropropane (TCP) in their water.
Granular Activated Carbon Contact Time: Why Bed Depth Matters More for TCP Than for Taste
When considering treatment for 1,2,3-TCP, a chlorinated solvent known to persist in water supplies, the contact time within a granular activated carbon bed takes precedence over taste-based factors. Unlike contaminants that influence flavor or odor, TCP’s molecular structure requires sufficient exposure within the carbon media for effective interaction. A deeper carbon bed increases contact time, improving adsorption potential for TCP, which is less volatile and more chemically stable than many taste-related compounds.
How a Soil Fumigant Impurity from the 1950s-1980s Reached Deep Groundwater Decades Later
1,2,3-trichloropropane originated primarily as a contaminant in soil fumigants used extensively from the mid-20th century through the 1980s. Its chemical stability and low degradation rate allowed it to leach downward, reaching groundwater and remaining detectable long after the cessation of fumigant use. In regions like Roanoke City served by surface water systems, residual TCP may be present due to environmental transport rather than recent sources.
The Household or Facility Symptoms That Do and Do Not Point to This Problem
- Symptoms not linked to 1,2,3-TCP: Changes in water taste, odor, or appearance are unlikely indicators because TCP is generally undetectable by sensory evaluation.
- Possible symptom-related concerns: Potential staining or corrosion are not typical effects of TCP but may relate to other water characteristics. Absence of such signs does not confirm or rule out TCP presence.
- Essential insight: Because TCP is chemically distinct from common taste-affecting or staining compounds, households should not rely on sensory cues to evaluate this contaminant.
How Many Samples and Wells Stand Behind the Figures, and What a Small Sample Means
The EPA’s Unregulated Contaminant Monitoring Rule (UCMR3) data for 2013-2015 covering the Western Virginia Water Authority system—which supplies Roanoke City—show 41 samples tested for 1,2,3-TCP with zero detections above the reporting level of 0.03 micrograms per liter (µg/L). This system serves approximately 182,700 people through 67,598 connections. While the sample size provides useful system-level information, it does not substitute for testing an individual household’s water, as localized conditions and plumbing materials can influence actual concentrations.
Why 1,2,3-Trichloropropane Resists Air Stripping and What That Means for Treatment Choice
Unlike some volatile organic compounds, 1,2,3-TCP resists removal through air stripping due to its low volatility and chemical stability. This resistance limits the effectiveness of aeration-based treatment methods commonly used for other solvents. Consequently, treatment options must focus on adsorption or filtration technologies capable of targeting TCP molecules at very low concentrations. This technical requirement narrows viable approaches for households considering water treatment.
For consumers weighing technical treatment paths, the Pentair 1,2,3-TCP Filter ships ready to configure and offers a documented solution specifically designed to address TCP in residential water supplies.
Next step: The single test to order is a laboratory analysis for 1,2,3-trichloropropane concentration in your household water. Measuring this will clarify whether TCP is present above the reporting level and inform which treatment approach is appropriate.
A result showing no detection of 1,2,3-TCP provides assurance consistent with area system data, enabling an informed choice between treatment options. Detectable TCP levels would support using targeted filtration technology like the Pentair system.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-12-17. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Western Virginia Water Authority (VA2770900), VA: 41 results across 1 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level