VOCs in well water: benzene, TCE, MTBE and limits
VOCs (volatile organic compounds) are man-made chemicals from fuel, solvents and industry. Most wells have none. Any detection is worth finding the source, and above the limit you should use bottled water for drinking and cooking.
- US (EPA), µg/L
- Benzene 5, trichloroethylene (TCE) 5, tetrachloroethylene (PCE) 5, vinyl chloride 2, carbon tetrachloride 5, dichloromethane 5, toluene 1,000, ethylbenzene 700, xylenes 10,000, total trihalomethanes 80. MTBE has no limit; EPA advises 20 to 40 for taste and smell.
- Ontario, µg/L
- Benzene 1, TCE 5, PCE 10, vinyl chloride 1, carbon tetrachloride 2, dichloromethane 50, toluene 60, ethylbenzene 140, xylenes 90, trihalomethanes 100.
What it is
VOCs evaporate easily, so they move from water into the air when you shower, wash dishes or do laundry. They reach wells from leaking fuel tanks and gas stations (benzene, toluene, ethylbenzene, xylenes and MTBE), from dry cleaners and degreasers (TCE and PCE, which break down into vinyl chloride), and from landfills and industry. Trihalomethanes such as chloroform form when chlorine reacts with natural organic matter, for example after shock chlorination. Labs report VOCs in µg/L, the same as parts per billion.
What your number means
- Not detectedBelow the reporting limit
The result you want. Most wells have no VOCs.
- Worth a lookDetected, below the limit
Something man-made is reaching the well. Retest, and ask your health department about nearby fuel or solvent sources.
- Above limitAbove the limit
Use bottled water for drinking and cooking, keep showers short and ventilated, and contact your health department.
What to do
- Above a limit, switch to bottled water for drinking, cooking and infant formula right away.
- Contact your health department. They can help find the source and may know about nearby contamination.
- Ask about whole house carbon treatment certified for the specific VOC. Because VOCs evaporate in the shower, a filter only at the kitchen tap isn't enough at high levels.
- If MTBE or benzene is found, ask about nearby fuel tanks, gas stations or spills.
- If chloroform or other trihalomethanes show up after shock chlorinating, retest a few weeks later. They often fade once the chlorine is gone.
How often to test
Once, and every few years if you live near a gas station, dry cleaner, landfill, industrial site or a busy road with fuel spills. Retest after any nearby spill.
Common questions
Why does a VOC in water matter in the shower?
VOCs evaporate easily, so hot water releases them into the air you breathe. That is why whole house treatment is often recommended for VOCs above the limit.
Is chloroform in well water dangerous?
Chloroform is a trihalomethane. Small amounts often appear after shock chlorination and fade later. If it stays, or the total trihalomethanes are above 80 µg/L, find the source and ask about a certified carbon filter.
Sources: EPA drinking water regulations; Ontario Drinking Water Quality Standards (O. Reg. 169/03). Limits checked November 2026. We review these standards every month.