How Safe Is Somerville's Tap Water?

SOMERVILLE, MA — As the temperatures stretch above the 80s in Somerville folks are drinking a lot more water. But how safe is the water from the tap? Should you be buying more bottled water?

A look at the annual MWRA state testing of the water coming from the Quabbin and Wachusett reservoirs to Somerville says the water tests normal. In a letter, DPW Commissioner Stan Koty said in 2016 21 water samples were tested each week for total coliform bacteria – bacteria found in soil, a water supply that has been influenced by surface water and human or animal waste.

Total coliform was detected in one sample in October, but repeat samples upstream and downstream yielded no further detection. The sample was 1.1 percent of all samples that month below the allowable percentage, Koty said. The EPA requires that no more than 5 percent of samples in a month be positive.

Somerville has been taking steps to maintain its distribution system. Much of the 125 miles of water mains was built in the late 1800s and early 1900s, and the city has been upgrading and replacing older unlined water mains. In 2015, the city replaced approximately 8,100 feet of older water mains and cleaned and lined about 1,200 feet of mains. In addition, Somerville flushed over 180,000 feet of pipe to maintain water quality and fire flows.

In terms of lead, last year Somerville tested at 9.48 parts per billion, well below the "Action Level" of 15 parts per billion, according to Koty. The city removed more than 20 lead service lines – pipes that connect buildings to the outside water main – in 2016, and continues to focus on removing lead services from the existing infrastructure.

Through the Department of Environmental Protection's lead tap sampling program, Somerville tests water taps in 15 houses. It has also applied to the MWRA's "Lead Service Line Reduction Program."

The MWRA recommends homeowners replace services lines from before the 1940s, as they are made from lead. This is the main source of lead in tap water in homes with older service lines. Removing lead service lines is a priority to reduce the potential for lead exposure, particularly if a pregnant woman or child lives in the home, the MWRA said.

If you think your pipes might be from before the 40s, the state has a couple recommendations to avoid lead exposure, including using cold water to cook and letting the water run until it gets cold if you haven't used the sink for six hours or more. (See more here). But chances are, they say, you're not going to get lead poisoning from drinking the tap water.

The Quabbin reservoir water goes through treatment at the John J. Carroll Water Treatment Plant in Marlborough. There it's treated with ozone, ultraviolet disinfection and fluoride is added and then mono-chloramine, a mild and long-lasting disinfectant combining chlorine and ammonia to protect the water as it travels through miles of pipelines to your home, according to the MWRA.

How reliable are the state's results? Pretty reliable, experts say.

"In general, the quality of local water straight from the tap is excellent and state water test results are reliable. There are high-profile cases where this clearly has not been the case -- most notably in Flint, Michigan -- but people in communities such as Newton and Brookline [and Arlington] have good reason to be confident in the quality of their tap water and that local officials will take action quickly if the quality is threatened," said Jim Salzman author of "Drinking Water: A History."

Jenna Fisher (Patch Staff) contributed to this report.

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