Total Trihalomethanes (TTHM)

Important Information About Your Drinking Water

Please have this information translated or contact the Plainville Water Department to have it translated.

Our drinking water system exceeded a drinking water standard, or maximum contamination level (MCL), for a water disinfection byproduct (DBP). Testing results came from routine monitoring of drinking water contaminants from January/March 2023. The level of total trihalomethane (TTHM) averaged at our system's 151 West Bacon St was 80.75 parts per billion (ppb) or micrograms per liter (ug/L). The standard is 80 ppb for TTHM. The system concentrations are determined by averaging their concentrations in all samples collected at each sampling location for the past 12 months.  

Although the elevated levels of TTHMs are of concern, this is not an emergency, and an alternative source of water is not necessary. If it had been, you would have been notified immediately. As our customers, you have a right to know what happened and what we are doing to correct this situation. 

*ppb = parts per billion

Image of Total Trihalomethanes Chart dated May 22, 2023

What does this mean?

This is not an emergency. If it had been an emergency, you would have been notified within 24 hours. TTHM are four volatile organic chemicals which form when disinfectants react with natural organic matter in the water.

Some people who drink water containing trihalomethanes in excess of the MCL over many years may experience problems with their liver, kidneys, or central nervous system, and may have an increased risk of getting cancer.

What is being done?

The Plainville Water Department is flushing the system and will be lowering the chlorine residual throughout the system. We anticipate resolving the elevated levels of TTHM within 90 days.

For more information, contact the Plainville Water Department at (508) 695-6871.

What should I do?

There is nothing you need to do. You do not need to boil your water or take other corrective actions. If a situation arises where the water is no longer safe to drink, you will be notified within 24 hours. You can choose to limit the amount of tap water if you are pregnant, may become pregnant or are giving water to young children. For example, you can use water from another source, such as bottled water. You can let water sit in a pitcher overnight to allow the TTHM chemicals to leave the water. Most TTHM are volatile and will easily evaporate from the water at room temperature.

While breast milk can be a source of TTHM exposure for infants, The Centers for Disease Control and Prevention recommend that nursing mothers continue to breastfeed their babies because of the numerous protective health benefits, despite the potential presence of environmental contaminants. 

You can also use home water filters to reduce exposures. (See MassDEP's TTHM in Drinking Water Information for Consumers Fact Sheet -

If you have questions about your water system's operation, water quality monitoring, or response to this issue, please contact the system operator directly at (508) 695-6871

If you have questions about the drinking water regulations or health risks posed by these contaminants, you can contact the MassDEP Drinking Water Program at: or (617) 292-5770

If you have questions about specific symptoms, you can contact your doctor or other health care provider. If you have general questions about your health, you can contact the Massachusetts Department of Public Health at (617) 624-5757. Further information is available in the MassDEP's TTHM in Drinking Water Information for Consumers Fact Sheet (https://www /download).